MOSCOW — Moscow’s first mayoral election in a decade ended with a narrow victory for the appointed incumbent Sunday, according to preliminary results. But his main challenger, one of President Vladimir V. Putin’s most prominent critics, claimed that he had won enough votes to force a runoff, and he warned of efforts to falsify the outcome of a race that proved to be much closer than expected.
The election was widely seen as an unusually competitive test of Putin’s power, following mass protests in 2011 and 2012 over the conduct of national elections, including Putin’s third campaign for the presidency. Sergei S. Sobyanin, the incumbent and Kremlin insider who was appointed mayor in 2010, appeared headed to a new five-year term, though hardly with a thunderous endorsement from voters, given his overwhelming advantages in the race.
Moments after the polls closed Sunday night, Alexei A. Navalny, the charismatic lawyer and blogger who has emerged as a potent opposition leader, said that his campaign’s exit polling indicated that Sobyanin had won fewer votes than the 50 percent needed to prevent a runoff.
With 98 percent of the ballots counted, Sobyanin’s tally hovered just above 51 percent, according to official but not yet final results announced early Monday. Navalny was running second with 27 percent, followed by the Communist Party’s candidate, Ivan I. Melnikov, with nearly 11 percent. Three other candidates got around 3 percent each.
Navalny said his campaign’s polling indicated that he had won 35 percent, compared with about 46 percent for Sobyanin, depriving him of an outright victory.
Regardless of the final outcome, Navalny, 37, defied expectations for Russia’s beleaguered democratic opposition. And a challenge of the results by Navalny could lead to more popular unrest.