From the frozen streets of Russia’s Far East and Siberia to the grand plazas of Moscow and St. Petersburg, tens of thousands of Russians rallied in support of the jailed opposition leader Alexei Navalny on Saturday in the biggest nationwide showdown in years between the Kremlin and its opponents.

The demonstrations did not immediately pose a dire threat to President Vladimir Putin’s grip on power. But their broad scope, and the remarkable defiance displayed by many of the protesters, signaled widespread fatigue with the stagnant, corruption-plagued political order that Putin has presided over for two decades.

The protests began to unfold in the eastern regions of Russia, a country of 11 time zones, and they moved like a wave across the nation despite a heavy police presence and a drumbeat of menacing warnings on state media to stay away.