The Many Regions And Ethnic Groups Of the Soviet Union are calling for enhanced rights. Some of them, especially the Baltic republics of Latvia, Estonia and Lithuania, want all-out independence. Others seek increased autonomy that would wrest some control away from Moscow. Complicating this push for a realignment of power are ethnic clashes in several republics. Such militancy represents a bold challenge to the Soviet state. It threatens the central command in Moscow and may hasten the political demise of Mikhail S. Gorbachev. A proposed treaty defining the powers of the central government and the rights of the republics has further kindled the debate. Though the treaty improves the republics' stature, it makes secession difficult to achieve. How this conflict is resolved will help define the future shape of the Soviet Union.