Brazil's president faced a growing corruption scandal as voters began casting ballots Sunday and the latest polls showed slipping support may force him into a runoff to win a second term.

The scandal that has enveloped the administration of Luiz Inacio Lula da Silva erupted only weeks before the presidential election. Six members of Silva's Workers Party, including an old friend who ran his personal security detail, face arrest warrants for their alleged roles in an effort to buy damaging information about Silva's political opponents. Silva fired his campaign manager days before the election.

Newspapers ran front-page photos Sunday of piles of money allegedly used to buy the information. Local media reported the photos were leaked by federal police.

But many Brazilians seem willing to overlook the corruption allegations because they feel their lives have gotten better during Silva's four years in office. He has brought a stable economy and social programs that have lifted millions out of poverty.

Silva's main challenger, Geraldo Alckmin, promised "ethics will defeat corruption" when he voted Sunday in the upscale Morumbi district.

Silva also voted Sunday morning in the working class city of Sao Bernardo de Campo on the outskirts of Sao Paulo where he got his start as a labor leader.

"This is a glorious moment for Brazil because the election consolidates the democratic process," he said after voting.

New opinion polls on the eve of the election showed Silva's once-commanding lead dipping, suggesting the former radical union leader may not walk away with the more than 50 percent needed to achieve a first round victory and could be forced to campaign for another month amid the corruption allegations against his party.

Polls by Ibope and Datafolha released late Saturday showed Silva getting 49 percent and 50 percent of the valid votes, respectively. Earlier in the week, his support had reached 59 percent. He needs a majority to avoid a runoff on Oct. 29 which would mean another month of campaigning under the shadow of the corruption scandal.

Alckmin, of the centrist Social Democracy Party, received 37 and 38 percent, and far-left candidate Sen. Heloisa Helena was expected to get 9 percent in both polls.

Ibope interviewed nearly 3,000 people in 200 cities Friday and Saturday. Datafolha surveyed more than 14,500 people in nearly 400 cities on the same days. Both polls had a margin of error of 2 percentage points.

The polls were some of the first released after Silva made a much-criticized decision to skip the nationally televised presidential debate on Thursday.

Still Silva's efforts to reduce poverty play well in the slums of Sao Paulo and Rio de Janeiro.

"Zero Hunger," his expanded food stamp-like program, guarantees about $30 a month to virtually all poor families provided they vaccinate their children and keep them in school. It distributes $325 million a month to 45 million of Brazil's 187 million citizens. The program has helped millions of Brazilians out of poverty, studies show.

A poor farmer's son who became a fiery union leader and was later elected as Brazil's first leftist president, Silva surprised many by governing as a moderate once taking office. His deft handling of the economy won him backing on Wall Street and in Brazil's shantytowns. His second-term priorities include reforming the tax and labor rules.

More than 125 million Brazilians were expected to vote for the president, governors for all 26 states and the federal district, all 513 federal deputies of the lower house and 27 of the 81 Senate seats.

Voting is mandatory in Brazil and those who fail to justify their absence both within Brazil and abroad may be fined.