MOSCOW (Reuters) - Vladimir Putin filed candidacy papers for a March 4 presidential election on Wednesday while his opponents prepared for more protests over a parliamentary vote they say was rigged in favor of his ruling party. Some 5,000 people turned out Monday night for the largest opposition protest in Moscow in years, many chanting "Russia without Putin ." More than 300 were detained Tuesday after a similar demonstration. Putin submitted his registration documents in a brief and nearly silent visit to the Central Election Commission headquarters in a lane near the Kremlin.