(Reuters) - Russia holds a presidential election Sunday. Here are some key facts about the five candidates.
VLADIMIR PUTIN, 59, prime minister.
A longtime KGB officer who was stationed in East Germany during the Soviet era, Putin shifted to a career in government after returning to his native St Petersburg after the fall of the Berlin Wall. He moved to Moscow in 1996 and began a swift rise to power, becoming head of the FSB security service and then prime minister.
President Boris Yeltsin resigned on December 31, 1999, making Putin interim president. He was elected to the first of two four-year terms in March 2000.
He presided over an oil-fueled boom that improved living standards and restored pride among many Russians, but critics say he curtailed freedoms and let corruption thrive.
Facing a constitutional bar on serving a third straight presidential term in 2008, Putin tapped Dmitry Medvedev as his favored successor and became prime minister. But he is still seen as the paramount leader.
He faces persistent street protests stoked by anger over suspicions of fraud in a parliamentary election in December and dismay over the prospect of him dominating the political scene for years to come.
Poll rating: 66 percent. In a survey conducted February 17-20 by Russia's biggest independent polling agency, the Levada Center, 66 percent of those who planned to vote and had chosen a candidate said they would vote for Putin.
GENNADY ZYUGANOV, 67, Communist Party leader.
A former high school physics teacher, Zyuganov climbed the rungs of power as an apparatchik in the Soviet Union's all-powerful Communist party just as the country was disintegrating. He has headed the Russian Communist party since 1993.
He has run for president three times before, coming second each time. He came closest to victory in 1996, when he forced President Boris Yeltsin into a run-off vote. He lost to Putin in 2000 and to Dmitry Medvedev, the current president, in 2008.
Zyuganov has resorted at times to nationalism to try to broaden his party's appeal and has sought to bring more young people into a party popular with older Russians nostalgic for the Soviet era.
He has also sought to make inroads among the mostly urban, middle-class Russians who have turned out for the biggest protests of Putin's 12-year rule.
Zyuganov, who promises a more equal distribution of Russia's wealth from oil and gas revenues if elected, has vowed this will be his last presidential campaign.
Poll rating: 15 percent (Levada).
VLADIMIR ZHIRINOVSKY, 65, leader of nationalist LDPR party.
Known for his flamboyant, nationalist rhetoric, Zhirinovsky was born in then-Soviet Kazakhstan. He has a degree in Turkish studies and is fluent in the language. He ran for the Russian presidency in 1991, months before the Soviet Union broke up, coming in third place in a vote won by Boris Yeltsin.
Zhirinovsky's party won nearly a quarter of the vote in Russia's 1993 parliamentary election, stoking fears of a rise of virulent nationalism. His attraction is strong for many Russians but his rhetoric has been taken less seriously in recent years. He ran unsuccessfully for president in 1996, 2000 and 2008.
He played the role of court jester during Putin's 2000-2008 presidency. His party supported the Kremlin line in most parliamentary votes, deepening suspicions he was a puppet used by Putin to steer the nationalist vote into safe channels.
Poll rating: 8 percent (Levada).
MIKHAIL PROKHOROV, 46, billionaire.
Prokhorov, ranked Russia's third-richest man by Forbes magazine with a fortune of $18 billion, owns aluminum, gold and banking assets and the New Jersey Nets basketball team.
He is the youngest candidate and the only first-time candidate, having entered politics just last year in a brief stint as head of a Kremlin-backed party.
Prokhorov has conducted a lively campaign, dropping in on a children's basketball clinic and rapping on television, and appeals to some upwardly mobile Russians tired of Putin.
However, his chances are undermined by the resentment many Russians feel toward the "oligarchs" who profited from the privatizations of the 1990s and suspicions that he is in the race to help Putin.
Prokhorov denies the accusations but has said he would not rule out becoming prime minister if Putin wins the election and is ready for reform.
Long known for jet-set travel and parties, he says he is in politics for the long haul, and announced plans to create a new party just weeks before the election.
Poll rating: 6 percent (Levada).
SERGEI MIRONOV, 59, former upper parliament house speaker.
Mironov comes from Putin's hometown of St Petersburg, where he was a legislator in the city council for most of the 1990s after spending the last years of the Soviet Union working as a geophysicist in Mongolia.
Long the leader of the socially oriented Just Russia party, seen as a Kremlin creation meant to provide a safe alternative to the dominant United Russia party, he was speaker of Russia's upper house of parliament from 2001 until 2011, when he was ousted by United Russia ahead of a December parliamentary election.
The parliament has been largely a rubber stamp for Putin's policies and Mironov espoused staunch loyalty to Putin until recently. He ran against Putin for president in 2004, but was quoted as saying he was in the race to support Putin and that "we all want" Putin to win. Mironov won less than 1 percent.
Poll rating: 5 percent (Levada).
Writing by Steve Gutterman; Editing by Andrew Osborn