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|  | MacArthur, Tom | R | NJ | U.S. House | 2015 – 2019 |
| | Macdonald, Torbert Hart | D | MA | U.S. House | 1955 – 1977 |
| | Mace, Nancy | R | SC | U.S. House | 2021 – 2023 |
| | Macgregor, Clark | R | MN | U.S. House | 1961 – 1972 |
| | Machen, Hervey Gilbert | D | MD | U.S. House | 1965 – 1969 |
| | Machrowicz, Thaddeus Michael | D | MI | U.S. House | 1951 – 1961 |
| | Machtley, Ronald K. | R | RI | U.S. House | 1989 – 1995 |
| | Mack, Connie | R | FL | U.S. House | 2005 – 2013 |
| | Mack, Connie | R | FL | U.S. Senate | 1983 – 2001 |
| | Mack, Peter Francis, Jr. | D | IL | U.S. House | 1949 – 1963 |
| | Mack, Russell Vernon | R | WA | U.S. House | 1947 – 1960 |
| | Mackay, James Armstrong | D | GA | U.S. House | 1965 – 1967 |
| | Mackay, Kenneth Hood, Jr. (Buddy) | D | FL | U.S. House | 1983 – 1989 |
| | Mackie, John C. | D | MI | U.S. House | 1965 – 1967 |
| | Mackinnon, George Edward | R | MN | U.S. House | 1947 – 1949 |
| | Macy, William Kingsland | R | NY | U.S. House | 1947 – 1952 |
| | Madden, Ray John | D | IN | U.S. House | 1945 – 1977 |
| | Madigan, Edward Rell | R | IL | U.S. House | 1973 – 1991 |
| | Maffei, Dan | D | NY | U.S. House | 2009 – 2015 |
| | Magee, Clare | D | MO | U.S. House | 1949 – 1953 |
| | Magnuson, Donald Hammer | D | WA | U.S. House | 1953 – 1963 |
| | Magnuson, Warren Grant | D | WA | U.S. Senate | 1945 – 1981 |
| | Maguire, Gene Andrew | D | NJ | U.S. House | 1975 – 1981 |
| | Mahon, George Herman | D | TX | U.S. House | 1945 – 1979 |
| | Mahoney, Tim | D | FL | U.S. House | 2007 – 2009 |
| | Mailliard, William Somers | R | CA | U.S. House | 1953 – 1974 |
| | Majette, Denise | D | GA | U.S. House | 2003 – 2005 |
| | Malinowski, Tom | D | NJ | U.S. House | 2019 – 2023 |
| | Mallary, Richard Walker | R | VT | U.S. House | 1972 – 1975 |
| | Malliotakis, Nicole | R | NY | U.S. House | 2021 – 2023 |
| | Malone, George Wilson | R | NV | U.S. Senate | 1947 – 1959 |
| | Maloney, Carolyn | D | NY | U.S. House | 1993 – 2023 |
| | Maloney, Franklin John | R | PA | U.S. House | 1947 – 1949 |
| | Maloney, James H. | D | CT | U.S. House | 1997 – 2003 |
| | Maloney, Paul Herbert | D | LA | U.S. House | 1945 – 1947 |
| | Maloney, Sean | D | NY | U.S. House | 2013 – 2023 |
| | Manasco, Carter | D | AL | U.S. House | 1945 – 1949 |
| | Manchin, Joe | D | WV | U.S. Senate | 2010 – 2025 |
| | Mankin, Helen Douglas | D | GA | U.S. House | 1946 – 1947 |
| | Mann, David Scott | D | OH | U.S. House | 1993 – 1995 |
| | Mann, James Robert | D | SC | U.S. House | 1969 – 1979 |
| | Mann, Tracey | R | KS | U.S. House | 2021 – 2023 |
| | Manning, Kathy | D | NC | U.S. House | 2021 – 2023 |
| | Mansfield, Joseph Jefferson | D | TX | U.S. House | 1917 – 1947 |
| | Mansfield, Michael Joseph (Mike) | D | MT | U.S. Senate | 1945 – 1977 |
| | Manton, Thomas Joseph | D | NY | U.S. House | 1985 – 1999 |
| | Manzullo, Donald | R | IL | U.S. House | 1993 – 2013 |
| | Maraziti, Joseph James | R | NJ | U.S. House | 1973 – 1975 |
| | Marcantonio, Vito Anthony | AM LAB | NY | U.S. House | 1939 – 1952 |
| | Marchant, Kenny | R | TX | U.S. House | 2005 – 2021 |
| | Margolies-Mezvinsky, Marjorie | D | PA | U.S. House | 1993 – 1995 |
| | Marino, Tom | R | PA | U.S. House | 2011 – 2021 |
| | Markey, Betsy | D | CO | U.S. House | 2009 – 2011 |
| | Markey, Edward | D | MA | U.S. Senate | 1977 – 2027 |
| | Marks, Marc Lincoln | R | PA | U.S. House | 1977 – 1983 |
| | Marlenee, Ronald Charles | R | MT | U.S. House | 1977 – 1993 |
| | Marriott, David Daniel | R | UT | U.S. House | 1977 – 1985 |
| | Marsalis, John Henry | D | CO | U.S. House | 1949 – 1952 |
| | Marsh, John Otho, Jr. | D | VA | U.S. House | 1963 – 1972 |
| | Marshall, Fred | D | MN | U.S. House | 1949 – 1963 |
| | Marshall, Jim | D | GA | U.S. House | 2003 – 2011 |
| | Marshall, Roger | R | KS | U.S. House | 2017 – 2027 |
| | Martin, David O'Brien | R | NY | U.S. House | 1981 – 1993 |
| | Martin, David Thomas | R | NE | U.S. House | 1961 – 1975 |
| | Martin, Edward | R | PA | U.S. Senate | 1947 – 1959 |
| | Martin, James Douglas | R | AL | U.S. House | 1965 – 1967 |
| | Martin, James Grubbs | R | NC | U.S. House | 1973 – 1985 |
| | Martin, Joseph William, Jr. | R | MA | U.S. House | 1925 – 1967 |
| | Martin, Lynn Morley | R | IL | U.S. House | 1981 – 1991 |
| | Martin, Patrick Minor | R | CA | U.S. House | 1963 – 1965 |
| | Martin, Thomas Ellsworth | R | IA | U.S. Senate | 1939 – 1961 |
| | Martinez, Matthew Gilbert | D | CA | U.S. House | 1982 – 2001 |
| | Martinez, Mel | R | FL | U.S. Senate | 2005 – 2011 |
| | Martini, William J. | R | NJ | U.S. House | 1995 – 1997 |
| | Mascara, Frank R. | D | PA | U.S. House | 1995 – 2003 |
| | Mason, Noah Morgan | R | IL | U.S. House | 1945 – 1963 |
| | Massa, Eric | D | NY | U.S. House | 2009 – 2010 |
| | Massie, Thomas | R | KY | U.S. House | 2012 – 2023 |
| | Mast, Brian | R | FL | U.S. House | 2017 – 2023 |
| | Matheson, Jim | D | UT | U.S. House | 2001 – 2015 |
| | Mathews, Frank Asbury, Jr. | R | NJ | U.S. House | 1945 – 1949 |
| | Mathews, Harlan | D | TN | U.S. Senate | 1993 – 1995 |
| | Mathias, Charles McCurdy, Jr | R | MD | U.S. Senate | 1961 – 1987 |
| | Mathias, Robert Bruce | R | CA | U.S. House | 1967 – 1975 |
| | Mathis, Marvin Dawson | D | GA | U.S. House | 1971 – 1981 |
| | Matsui, Doris | D | CA | U.S. House | 2005 – 2023 |
| | Matsunaga, Spark Masayuki | D | HI | U.S. Senate | 1963 – 1990 |
| | Matthews, Donald Ray (Billy) | D | FL | U.S. House | 1953 – 1967 |
| | Mattingly, Mack Francis | R | GA | U.S. Senate | 1981 – 1987 |
| | Mattox, James Albon | D | TX | U.S. House | 1977 – 1983 |
| | Mavroules, Nicholas James | D | MA | U.S. House | 1979 – 1993 |
| | May, Andrew Jackson | D | KY | U.S. House | 1945 – 1947 |
| | May, Catherine Dean | R | WA | U.S. House | 1959 – 1972 |
| | May, Edwin Hyland, Jr. | R | CT | U.S. House | 1957 – 1959 |
| | Maybank, Burnet Rhett | D | SC | U.S. Senate | 1943 – 1954 |
| | Mayne, Wiley | R | IA | U.S. House | 1967 – 1975 |
| | Mazzoli, Romano Louis | D | KY | U.S. House | 1971 – 1995 |
| | McAdams, Ben | D | UT | U.S. House | 2019 – 2021 |
| | McBath, Lucy | D | GA | U.S. House | 2019 – 2023 |
| | McCain, John | R | AZ | U.S. Senate | 1983 – 2018 |
| | McCandless, Alfred A. | R | CA | U.S. House | 1983 – 1995 |
| | McCarran, Patrick Anthony (Pat) | D | NV | U.S. Senate | 1945 – 1954 |
| | McCarthy, Eugene Joseph | D | MN | U.S. Senate | 1949 – 1971 |
| | McCarthy, Joseph Raymond | R | WI | U.S. Senate | 1947 – 1957 |
| | McCarthy, Kevin | R | CA | U.S. House | 2007 – 2023 |
| | McCarthy, Richard Dean | D | NY | U.S. House | 1965 – 1971 |
| | McCaskill, Claire | D | MO | U.S. Senate | 2007 – 2019 |
| | McCaul, Michael | R | TX | U.S. House | 2005 – 2023 |
| | McClain, Lisa | R | MI | U.S. House | 2021 – 2023 |
| | McClellan, John Little | D | AR | U.S. Senate | 1943 – 1979 |
| | McClintock, Tom | R | CA | U.S. House | 2009 – 2023 |
| | McClory, Robert | R | IL | U.S. House | 1963 – 1983 |
| | McCloskey, Francis Xavier | D | IN | U.S. House | 1983 – 1995 |
| | McCloskey, Paul Norton, Jr. | R | CA | U.S. House | 1967 – 1983 |
| | McClure, James Albertus | R | ID | U.S. Senate | 1967 – 1991 |
| | McCollister, John Yetter | R | NE | U.S. House | 1971 – 1977 |
| | McCollum, Betty | D | MN | U.S. House | 2001 – 2023 |
| | McCollum, Bill, Jr. | R | FL | U.S. House | 1981 – 2001 |
| | McConnell, Mitch | R | KY | U.S. Senate | 1985 – 2027 |
| | McConnell, Samuel Kerns, Jr. | R | PA | U.S. House | 1945 – 1957 |
| | McCormack, John William | D | MA | U.S. House | 1928 – 1971 |
| | McCormack, Mike | D | WA | U.S. House | 1971 – 1981 |
| | McCotter, Thaddeus | R | MI | U.S. House | 2003 – 2012 |
| | McCowen, Edward Oscar | R | OH | U.S. House | 1945 – 1949 |
| | McCrery, Jim | R | LA | U.S. House | 1988 – 2009 |
| | McCulloch, William Moore | R | OH | U.S. House | 1947 – 1973 |
| | McCurdy, David Keith | D | OK | U.S. House | 1981 – 1995 |
| | McDade, Joseph Michael | R | PA | U.S. House | 1963 – 1999 |
| | McDermott, Jim | D | WA | U.S. House | 1989 – 2017 |
| | Mcdonald, Jack H. | R | MI | U.S. House | 1967 – 1973 |
| | Mcdonald, Lawrence Patton | D | GA | U.S. House | 1975 – 1983 |
| | Mcdonough, Gordon Leo | R | CA | U.S. House | 1945 – 1963 |
| | Mcdowell, Harris Brown, Jr. | D | DE | U.S. House | 1955 – 1967 |
| | Mcdowell, John Ralph | R | PA | U.S. House | 1947 – 1949 |
| | McEachin, A. | D | VA | U.S. House | 2017 – 2022 |
| | Mcewen, Bob | R | OH | U.S. House | 1981 – 1993 |
| | Mcewen, Robert Cameron | R | NY | U.S. House | 1965 – 1981 |
| | Mcfall, John Joseph | D | CA | U.S. House | 1957 – 1979 |
| | Mcfarland, Ernest William | D | AZ | U.S. Senate | 1945 – 1953 |
| | Mcgarvey, Robert Neill | R | PA | U.S. House | 1947 – 1949 |
| | Mcgee, Gale William | D | WY | U.S. Senate | 1959 – 1977 |
| | Mcgehee, Daniel Rayford | D | MS | U.S. House | 1945 – 1947 |
| | Mcginley, Donald Francis | D | NE | U.S. House | 1959 – 1961 |
| | Mcglinchey, Herbert Joseph | D | PA | U.S. House | 1945 – 1947 |
| | Mcgovern, George Stanley | D | SD | U.S. Senate | 1957 – 1981 |
| | McGovern, Jim | D | MA | U.S. House | 1997 – 2023 |
| | Mcgrath, Christopher Columbus | D | NY | U.S. House | 1949 – 1953 |
| | Mcgrath, James Howard | D | RI | U.S. Senate | 1947 – 1949 |
| | Mcgrath, Raymond Joseph | R | NY | U.S. House | 1981 – 1993 |
| | Mcgrath, Thomas Charles, Jr. | D | NJ | U.S. House | 1965 – 1967 |
| | Mcgregor, J. Harry | R | OH | U.S. House | 1945 – 1958 |
| | Mcguire, John Andrew | D | CT | U.S. House | 1949 – 1953 |
| | McHale, Paul | D | PA | U.S. House | 1993 – 1999 |
| | McHenry, Patrick | R | NC | U.S. House | 2005 – 2023 |
| | McHugh, John M. | R | NY | U.S. House | 1993 – 2011 |
| | Mchugh, Matthew Francis | D | NY | U.S. House | 1975 – 1993 |
| | McInnis, Scott | R | CO | U.S. House | 1993 – 2005 |
| | Mcintire, Clifford Guy | R | ME | U.S. House | 1952 – 1965 |
| | McIntosh, David M. | R | IN | U.S. House | 1995 – 2001 |
| | Mcintosh, Robert John | R | MI | U.S. House | 1957 – 1959 |
| | McIntyre, Mike | D | NC | U.S. House | 1997 – 2015 |
| | Mcintyre, Thomas James | D | NH | U.S. Senate | 1963 – 1979 |
| | Mckay, Koln Gunn | D | UT | U.S. House | 1971 – 1981 |
| | Mckellar, Kenneth Douglas | D | TN | U.S. Senate | 1945 – 1953 |
| | Mckenzie, Charles Edgar | D | LA | U.S. House | 1945 – 1947 |
| | McKeon, Howard "Buck" | R | CA | U.S. House | 1993 – 2015 |
| | Mckernan, John Rettie, Jr. | R | ME | U.S. House | 1983 – 1987 |
| | Mckevitt, James Douglas (Mike) | R | CO | U.S. House | 1971 – 1973 |
| | McKinley, David | R | WV | U.S. House | 2011 – 2023 |
| | McKinney, Cynthia A. | D | GA | U.S. House | 1993 – 2007 |
| | Mckinney, Stewart Brett | R | CT | U.S. House | 1971 – 1987 |
| | Mckinnon, Clinton Dotson | D | CA | U.S. House | 1949 – 1953 |
| | Mckneally, Martin Boswell | R | NY | U.S. House | 1969 – 1972 |
| | Mcloskey, Robert Thaddeus | R | IL | U.S. House | 1963 – 1965 |
| | Mcmahon, Brien | D | CT | U.S. Senate | 1945 – 1952 |
| | Mcmahon, Gregory | R | NY | U.S. House | 1947 – 1949 |
| | McMahon, Michael E. | D | NY | U.S. House | 2009 – 2011 |
| | McMillan, J. Alex, III | R | NC | U.S. House | 1985 – 1995 |
| | Mcmillan, John Lanneau | D | SC | U.S. House | 1945 – 1973 |
| | Mcmillen, Charles Thomas | D | MD | U.S. House | 1987 – 1993 |
| | Mcmillen, Rolla Coral | R | IL | U.S. House | 1945 – 1951 |
| | Mcmullen, Chester Bartow | D | FL | U.S. House | 1951 – 1953 |
| | Mcnamara, Patrick Vincent | D | MI | U.S. Senate | 1955 – 1966 |
| | McNerney, Jerry | D | CA | U.S. House | 2007 – 2023 |
| | Mcnulty, James Francis, Jr. | D | AZ | U.S. House | 1983 – 1985 |
| | McNulty, Michael R. | D | NY | U.S. House | 1989 – 2009 |
| | McSally, Martha | R | AZ | U.S. Senate | 2015 – 2020 |
| | Mcspadden, Clem Rogers | D | OK | U.S. House | 1973 – 1975 |
| | Mcsween, Harold Barnett | D | LA | U.S. House | 1959 – 1963 |
| | Mcsweeney, John | D | OH | U.S. House | 1949 – 1952 |
| | Mcvey, Walter Lewis, Jr. | R | KS | U.S. House | 1961 – 1963 |
| | Mcvey, William Estus | R | IL | U.S. House | 1951 – 1958 |
| | Mcvicker, Roy Harrison | D | CO | U.S. House | 1965 – 1967 |
| | Mead, James Michael | D | NY | U.S. Senate | 1945 – 1947 |
| | Meade, Hugh Allen | D | MD | U.S. House | 1947 – 1949 |
| | Meade, Wendell Howes | R | KY | U.S. House | 1947 – 1949 |
| | Meader, George | R | MI | U.S. House | 1951 – 1965 |
| | Meadows, Mark | R | NC | U.S. House | 2013 – 2020 |
| | Mechem, Edwin Leard | R | NM | U.S. Senate | 1963 – 1964 |
| | Meeds, Lloyd | D | WA | U.S. House | 1965 – 1979 |
| | Meehan, Martin T. | D | MA | U.S. House | 1993 – 2007 |
| | Meehan, Patrick | R | PA | U.S. House | 2011 – 2018 |
| | Meek, Carrie P. | D | FL | U.S. House | 1993 – 2003 |
| | Meek, Kendrick B. | D | FL | U.S. House | 2003 – 2011 |
| | Meeks, Gregory | D | NY | U.S. House | 1998 – 2023 |
| | Meijer, Peter | R | MI | U.S. House | 2021 – 2023 |
| | Melancon, Charlie | D | LA | U.S. House | 2005 – 2011 |
| | Melcher, John | D | MT | U.S. Senate | 1969 – 1989 |
| | Menendez, Bob | D | NJ | U.S. Senate | 1993 – 2025 |
| | Meng, Grace | D | NY | U.S. House | 2013 – 2023 |
| | Merkley, Jeff | D | OR | U.S. Senate | 2009 – 2027 |
| | MERRILL, D. Bailey | R | IN | U.S. House | 1953 – 1955 |
| | Merrow, Chester Earl | R | NH | U.S. House | 1945 – 1963 |
| | Meskill, Thomas Joseph | R | CT | U.S. House | 1967 – 1972 |
| | Messer, Luke | R | IN | U.S. House | 2013 – 2019 |
| | Metcalf, Jack | R | WA | U.S. House | 1995 – 2001 |
| | Metcalf, Lee Warren | D | MT | U.S. Senate | 1953 – 1979 |
| | Metcalfe, Ralph Harold | D | IL | U.S. House | 1971 – 1979 |
| | Metzenbaum, Howard Morton | D | OH | U.S. Senate | 1974 – 1995 |
| | Meuser, Dan | R | PA | U.S. House | 2019 – 2023 |
| | Meyer, Herbert Alton | R | KS | U.S. House | 1947 – 1950 |
| | Meyer, William Henry | D | VT | U.S. House | 1959 – 1961 |
| | Meyers, Jan | R | KS | U.S. House | 1985 – 1997 |
| | Meyner, Helen Stevenson | D | NJ | U.S. House | 1975 – 1979 |
| | Mezvinsky, Edward Maurice | D | IA | U.S. House | 1973 – 1977 |
| | Mfume, Kweisi | D | MD | U.S. House | 2020 – 2023 |
| | Mica, Daniel Andrew | D | FL | U.S. House | 1979 – 1989 |
| | Mica, John L. | R | FL | U.S. House | 1993 – 2017 |
| | Michaud, Michael H. | D | ME | U.S. House | 2003 – 2015 |
| | Michel, Robert Henry | R | IL | U.S. House | 1957 – 1995 |
| | Michener, Earl Cory | R | MI | U.S. House | 1919 – 1951 |
| | Mikulski, Barbara A. | D | MD | U.S. Senate | 1977 – 2017 |
| | Mikva, Abner Joseph | D | IL | U.S. House | 1969 – 1981 |
| | Miles, John Esten | D | NM | U.S. House | 1949 – 1952 |
| | Milford, Dale | D | TX | U.S. House | 1973 – 1979 |
| | Millender-McDonald, Juanita | D | CA | U.S. House | 1996 – 2007 |
| | Miller, Arthur Lewis | R | NE | U.S. House | 1945 – 1959 |
| | Miller, Bert Henry | D | ID | U.S. Senate | 1949 – 1949 |
| | Miller, Brad | D | NC | U.S. House | 2003 – 2013 |
| | Miller, Candice S. | R | MI | U.S. House | 2003 – 2017 |
| | Miller, Carol | R | WV | U.S. House | 2019 – 2023 |
| | Miller, Clarence E. | R | OH | U.S. House | 1967 – 1993 |
| | Miller, Clement Woodnutt | D | CA | U.S. House | 1959 – 1962 |
| | Miller, Dan | R | FL | U.S. House | 1993 – 2003 |
| | Miller, Edward Tylor | R | MD | U.S. House | 1947 – 1959 |
| | Miller, George Paul | D | CA | U.S. House | 1945 – 1973 |
| | Miller, Howard Shultz | D | KS | U.S. House | 1953 – 1955 |
| | Miller, Jack Richard | R | IA | U.S. Senate | 1961 – 1973 |
| | Miller, Jeff | R | FL | U.S. House | 2001 – 2017 |
| | Miller, John Ripin | R | WA | U.S. House | 1985 – 1993 |
| | Miller, Mary | R | IL | U.S. House | 2021 – 2023 |
| | Miller, William Edward | R | NY | U.S. House | 1951 – 1965 |
| | Miller, William Jennings | R | CT | U.S. House | 1947 – 1949 |
| | Miller, Zell | D | GA | U.S. Senate | 2000 – 2005 |
| | Miller-Meeks, Mariannette | R | IA | U.S. House | 2021 – 2023 |
| | Milliken, William H., Jr. | R | PA | U.S. House | 1959 – 1965 |
| | Millikin, Eugene Donald | R | CO | U.S. Senate | 1945 – 1957 |
| | Mills, Wilbur Daigh | D | AR | U.S. House | 1945 – 1977 |
| | Mills, William Oswald | R | MD | U.S. House | 1971 – 1973 |
| | Mineta, Norman Yoshio | D | CA | U.S. House | 1975 – 1995 |
| | Minge, David | D | MN | U.S. House | 1993 – 2001 |
| | Minish, Joseph George | D | NJ | U.S. House | 1963 – 1985 |
| | Mink, Patsy Takemoto | D | HI | U.S. House | 1965 – 2002 |
| | Minnick, Walt | D | ID | U.S. House | 2009 – 2011 |
| | Minshall, William Edwin, Jr. | R | OH | U.S. House | 1955 – 1975 |
| | Mitchell, Donald Jerome | R | NY | U.S. House | 1973 – 1983 |
| | Mitchell, Edward Archibald | R | IN | U.S. House | 1947 – 1949 |
| | Mitchell, George John | D | ME | U.S. Senate | 1980 – 1995 |
| | Mitchell, Harlan Erwin | D | GA | U.S. House | 1958 – 1961 |
| | Mitchell, Harry E. | D | AZ | U.S. House | 2007 – 2011 |
| | Mitchell, Hugh Burnton | D | WA | U.S. House | 1945 – 1953 |
| | Mitchell, Parren James | D | MD | U.S. House | 1971 – 1987 |
| | Mitchell, Paul | R | MI | U.S. House | 2017 – 2021 |
| | Mize, Chester Louis | R | KS | U.S. House | 1965 – 1972 |
| | Mizell, Wilmer David | R | NC | U.S. House | 1969 – 1975 |
| | Moakley, John Joseph | D | MA | U.S. House | 1973 – 2001 |
| | Moeller, Walter Henry | D | OH | U.S. House | 1959 – 1967 |
| | Moffett, Anthony John, Jr. (Toby) | D | CT | U.S. House | 1975 – 1983 |
| | Molinari, Guy Victor | R | NY | U.S. House | 1981 – 1990 |
| | Molinari, Susan | R | NY | U.S. House | 1990 – 1997 |
| | Mollohan, Alan B. | D | WV | U.S. House | 1983 – 2011 |
| | Mollohan, Robert Homer | D | WV | U.S. House | 1953 – 1983 |
| | Monagan, John Stephen | D | CT | U.S. House | 1959 – 1973 |
| | Mondale, Walter Frederick | D | | U.S. Senate | 1964 – 1981 |
| | Monroney, Almer Stillwell Mike | D | OK | U.S. Senate | 1939 – 1969 |
| | Monson, David Smith | R | UT | U.S. House | 1985 – 1987 |
| | Montgomery, Gillespie V. (Sonny) | D | MS | U.S. House | 1967 – 1997 |
| | Montoya, Joseph Manuel | D | NM | U.S. Senate | 1957 – 1977 |
| | Moody, Arthur Edson Blair | D | MI | U.S. Senate | 1951 – 1952 |
| | Moody, James Montraville | D | WI | U.S. House | 1983 – 1993 |
| | Moolenaar, John | R | MI | U.S. House | 2015 – 2023 |
| | Mooney, Alex | R | WV | U.S. House | 2015 – 2023 |
| | Moore, Arch Alfred, Jr. | R | WV | U.S. House | 1957 – 1969 |
| | Moore, Barry | R | AL | U.S. House | 2021 – 2023 |
| | Moore, Blake D. | R | UT | U.S. House | 2021 – 2023 |
| | Moore, Dennis | D | KS | U.S. House | 1999 – 2011 |
| | Moore, Edward Hall | R | OK | U.S. Senate | 1943 – 1949 |
| | Moore, Gwen | D | WI | U.S. House | 2005 – 2023 |
| | Moore, William Henson, III | R | LA | U.S. House | 1975 – 1987 |
| | Moorehead, Tom Van Horn | R | OH | U.S. House | 1961 – 1963 |
| | Moorhead, Carlos John | R | CA | U.S. House | 1973 – 1997 |
| | Moorhead, William Singer | D | PA | U.S. House | 1959 – 1981 |
| | Moran, Jerry | R | KS | U.S. Senate | 1997 – 2023 |
| | Morano, Albert Paul | R | CT | U.S. House | 1951 – 1959 |
| | Morella, Constance A. | R | MD | U.S. House | 1987 – 2003 |
| | Morelle, Joseph | D | NY | U.S. House | 2018 – 2023 |
| | Morgan, Robert Burren | D | NC | U.S. Senate | 1975 – 1981 |
| | Morgan, Thomas Ellsworth | D | PA | U.S. House | 1945 – 1977 |
| | Morris, Thomas Gayle | D | NM | U.S. House | 1959 – 1969 |
| | Morris, Toby | D | OK | U.S. House | 1947 – 1961 |
| | Morrison, Bruce Andrew | D | CT | U.S. House | 1983 – 1991 |
| | Morrison, James Hobson | D | LA | U.S. House | 1945 – 1967 |
| | Morrison, Sidney Wallace | R | WA | U.S. House | 1981 – 1993 |
| | Morse, Frank Bradford | R | MA | U.S. House | 1961 – 1972 |
| | Morse, Wayne Lyman | D | OR | U.S. Senate | 1945 – 1969 |
| | Morton, Rogers Clark Ballard | R | MD | U.S. House | 1963 – 1971 |
| | Morton, Thruston Ballard | R | KY | U.S. Senate | 1947 – 1968 |
| | Moseley-Braun, Carol | D | IL | U.S. Senate | 1993 – 1999 |
| | Moses, John | D | ND | U.S. Senate | 1945 – 1945 |
| | Mosher, Charles Adams | R | OH | U.S. House | 1961 – 1977 |
| | Moss, Frank Edward | D | UT | U.S. Senate | 1959 – 1977 |
| | Moss, John Emerson | D | CA | U.S. House | 1953 – 1979 |
| | Mott, James Wheaton | R | OR | U.S. House | 1945 – 1945 |
| | Mottl, Ronald Milton | D | OH | U.S. House | 1975 – 1983 |
| | Moulder, Morgan Moore | D | MO | U.S. House | 1949 – 1963 |
| | Moulton, Seth | D | MA | U.S. House | 2015 – 2023 |
| | Moynihan, Daniel Patrick | D | NY | U.S. Senate | 1977 – 2001 |
| | Mrazek, Robert Jan | D | NY | U.S. House | 1983 – 1993 |
| | Mrvan, Frank J. | D | IN | U.S. House | 2021 – 2023 |
| | Mucarsel-Powell, Debbie | D | FL | U.S. House | 2019 – 2021 |
| | Muhlenberg, Frederick Augustus | R | PA | U.S. House | 1947 – 1949 |
| | Mullin, Markwayne | R | OK | U.S. House | 2013 – 2027 |
| | Multer, Abraham Jacob | D | NY | U.S. House | 1947 – 1967 |
| | Mulvaney, Mick | R | SC | U.S. House | 2011 – 2017 |
| | Mumma, Walter Mann | R | PA | U.S. House | 1951 – 1961 |
| | Mundt, Karl Earl | R | SD | U.S. Senate | 1945 – 1973 |
| | Murdock, John Robert | D | AZ | U.S. House | 1945 – 1953 |
| | Murdock, Orrice Abram, Jr. (Abe) | D | UT | U.S. Senate | 1933 – 1947 |
| | Murkowski, Frank Hughes | R | AK | U.S. Senate | 1981 – 2002 |
| | Murkowski, Lisa | R | AK | U.S. Senate | 2002 – 2023 |
| | Murphy, Austin John | D | PA | U.S. House | 1977 – 1995 |
| | Murphy, Christopher | D | CT | U.S. Senate | 2007 – 2025 |
| | Murphy, George Lloyd | R | CA | U.S. Senate | 1965 – 1971 |
| | Murphy, Greg | R | NC | U.S. House | 2019 – 2023 |
| | Murphy, James Joseph | D | NY | U.S. House | 1949 – 1953 |
| | Murphy, John Michael | D | NY | U.S. House | 1963 – 1981 |
| | Murphy, John William | D | PA | U.S. House | 1945 – 1946 |
| | Murphy, Maurice J., Jr | R | NH | U.S. Senate | 1962 – 1962 |
| | Murphy, Morgan Francis | D | IL | U.S. House | 1971 – 1981 |
| | Murphy, Patrick J. | D | PA | U.S. House | 2007 – 2011 |
| | Murphy, Patrick | D | FL | U.S. House | 2013 – 2017 |
| | Murphy, Scott | D | NY | U.S. House | 2009 – 2011 |
| | Murphy, Stephanie | D | FL | U.S. House | 2017 – 2023 |
| | Murphy, Tim | R | PA | U.S. House | 2003 – 2017 |
| | Murphy, William Thomas | D | IL | U.S. House | 1959 – 1971 |
| | Murray, James Cunningham | D | IL | U.S. House | 1955 – 1957 |
| | Murray, James Edward | D | MT | U.S. Senate | 1943 – 1961 |
| | Murray, Patty | D | WA | U.S. Senate | 1993 – 2023 |
| | Murray, Reid Fred | R | WI | U.S. House | 1945 – 1953 |
| | Murray, Thomas Jefferson | D | TN | U.S. House | 1943 – 1966 |
| | Murtha, John P. | D | PA | U.S. House | 1974 – 2010 |
| | Musgrave, Marilyn | R | CO | U.S. House | 2003 – 2009 |
| | Muskie, Edmund Sixtus | D | ME | U.S. Senate | 1959 – 1981 |
| | Musto, Raphael John | D | PA | U.S. House | 1980 – 1981 |
| | Myers, Francis John | D | PA | U.S. Senate | 1939 – 1951 |
| | Myers, Gary Arthur | R | PA | U.S. House | 1975 – 1979 |
| | Myers, John Thomas | R | IN | U.S. House | 1967 – 1997 |
| | Myers, Michael Joseph (Ozzie) | D | PA | U.S. House | 1977 – 1981 |
| | Myrick, Sue | R | NC | U.S. House | 1995 – 2013 |
| | Negrete McLeod, Gloria | D | CA | U.S. House | 2013 – 2015 |
| | Political Unknown Beats Out State Senator in Louisiana's 5th District | R | LA | U.S. House | 2013 – 2015 |
| | Rodgers, Cathy | R | WA | U.S. House | 2005 – 2023 |