UFA, Russia - Here on the southwestern edge of the Urals, a popular uprising against a regional government is posing one of the most significant challenges yet to President Vladimir V. Putin's political control, raising the possibility that civic protest may be spreading into Russia from its periphery. Heartened by the political upheavals in two of Russia's neighbors, Ukraine and Kyrgyzstan, thousands here have staged a series of demonstrations since February calling for the ouster of the president of the Bashkortostan region, Murtaza G. Rakhimov. An ally of President Putin, he has served as the leader of this largely Muslim...