By Steve Gutterman
MOSCOW (Reuters) - Russian opposition leader Alexei Navalny's troubles mounted on Wednesday when a court rejected his bid to push his main pro-Kremlin rival out of the Moscow mayoral race and an electoral official said Navalny himself might be disqualified.
Navalny, who emerged from a wave of anti-government protests that began in 2011 as the most popular opposition figure, was sentenced to five years in prison last month for theft after a trial he has said was President Vladimir Putin's revenge.
But he is free pending a ruling on the appeal against his politically charged conviction and is running for mayor of Moscow to try to show that Putin's opponents have popular support even though the protests have faded.
Needling Putin and Sergei Sobyanin, the acting Moscow mayor appointed by the Kremlin three years ago, Navalny claimed the Kremlin favorite had violated election rules by failing to receive Putin's formal consent to run in the September 8 vote.
Lawyers for Navalny ridiculed a document presented as proof - a copy of a letter from Sobyanin asking for Putin's approval, with the single word "approve" scrawled above a signature purported to be Putin's.
"This is no document," lawyer Nikolai Kuznetsov told Reuters at the court, saying that only a decree or order from Putin would have legal force and that the original was never produced. "The same thing could have been done on a cocktail napkin."
The judge retired for about 10 minutes and emerged to announce his ruling against Navalny's claim.
"We are not satisfied with this process because the judge refused to take into account our arguments," Kuznetsov said.
Meanwhile, authorities made clear it is Navalny who might be ejected from the race, which pits him against a loyal and experienced politician touted as a potential future prime minister under Putin, who started a six-year third term in 2012.
Moscow elections chief Valentin Gorbunov said Navalny's team had committed campaign violations and that the city electoral commission would likely meet soon to discuss their severity and potential consequences, state-run news agency RIA reported.
"If the violations exceed the legally established norm, the question of revoking the registration of the candidate Navalny will emerge," RIA quoted Gorbunov as saying.
Electoral officials said checks had established that Navalny's campaign distributed materials that were paid for with funding from outside his campaign chest, RIA reported.
Last week, Russian prosecutors accused Navalny of illegally receiving foreign funding for his campaign, which he denied.
Navalny, 37, said the allegations were meant to discredit him and showed the Kremlin was worried his campaign was reducing Sobyanin's big lead in opinion polls. He says he is the one facing a campaign of dirty tricks.
Blaming what he claimed was pressure from Sobyanin's administration, he said on Tuesday a contract with a popular Russian social-networking site had been abandoned and talks with a radio station on airing his campaign ads had fallen through.
Polls suggest Navalny has no chance of winning, but a strong showing for the activist and anti-corruption blogger, whose description of ruling United Russia as a "party of swindlers and thieves" became a mantra at protests, would embarrass Putin.
Alexei Roshchin, a veteran campaign adviser and sociologist, said Navalny might be disqualified if Kremlin officials feared Sobyanin might fall short of the majority - 50 percent plus one vote - the he needs to avoid a runoff.
A decisive victory over Navalny would be a boon for Sobyanin, 55, who is widely believed to have called the early election in order to increase his legitimacy by becoming an elected official instead of an appointee.
(Additional reporting by Denis Dyomkin and Maria Tsvetkova; Editing by Timothy Heritage and Jon Boyle)