Voting began Sunday in presidential elections that are likely to return Vladimir Putin to the Kremlin for a record third six-year term.

As voting started, over 200,000 volunteer poll watchers swung into action, hoping to reduce fraud, like that cited in the December 4 parliamentary elections.

Another 600,000 Internet users have registered to monitor web cameras installed in all of Russia's nearly 100,000 polling stations.

Mr. Putin, Russia's current prime minister, is the leading candidate for the job. Latest opinion polls show that 80 percent of Russians believe he will return to the presidency, and 57 percent consider him the nation's leader, even though Dmitry Medvedev is officially president. He served two terms as president, from 2000 to 2008, before becoming prime minister.

An independent public opinion poll ahead of the election suggests that Mr. Putin is expected to avoid a runoff election with 62 to 66 percent of the vote.

However, during the election campaign Mr. Putin faced unprecedented opposition protests across the country against him and his ruling party.

Hundreds of thousands of Russians have taken to the streets since the parliamentary vote, claiming the party won by ballot stuffing and vote rigging — charges the party denies.

Since that vote, election officials have rejected almost all complaints and judges have ruled against almost all legal challenges. In addition, the Kremlin has fired four regional governors where the vote for the ruling party was below average.

Mr. Putin faces four challengers, most of whom are familiar faces in Russian politics. Communist Party head Gennady Zyuganov is expected to place second in the vote, while nationalist Vladimir Zhirinovsky and billionaire Mikhail Prokhorov, a newcomer, are expected to battle for third place. Former Putin ally Sergei Mironov placed last in the 2004 presidential election and is expected to do so again.

Leaders of the street opposition predict that election officials will declare a Putin victory shortly after the polls close. They are organizing mass protests for Monday in Moscow and Russia's other big cities.