BRASILIA, Brazil – Brazil’s leftist president, Luiz Inacio Lula da Silva, led his main challenger, Sao Paulo state Gov. Geraldo Alckmin, in his bid for re-election Sunday, but was falling short of the simple majority of votes needed to avoid a runoff, early results showed.

With 43 percent of the ballots counted, President Silva had 47 percent of the vote compared to 43 percent for Gov. Alckmin, election authorities said. Sen. Heloisa Helena had 7 percent, and lesser-known candidates were splitting the rest.

Silva, who brought economic stability and anti-poverty programs to Brazil but was dogged by corruption allegations, needs 50 percent plus one vote to win the contest Sunday. If he fails to get these numbers, he and Alckmin will head to a runoff on Oct. 29.

Earlier Sunday, Silva sounded confident after voting in the industrial town of Sao Bernardo Do Campo where he rose to prominence as a labor leader.

For months, polls have shown Silva easily winning a first-round victory. But Silva saw his once-commanding lead plummet on the eve of the vote, as his Workers’ Party was battered by allegations that party officials tried to buy a mysterious dossier that apparently contained incriminating information about a political rival.

Major newspapers ran front-page photos over the weekend showing piles of money allegedly meant to buy information showing corrupt dealings by an opponent. Local media reported the photos were leaked by federal police.

Silva’s party claimed that Alckmin’s supporters were involved, and filed a complaint Sunday with a judge demanding that Alckmin’s candidacy be declared invalid because of the leak. The judge has said he would consider the case. Alckmin’s campaign has denied involvement.

Six members of Silva’s party, including an old friend who ran his personal security detail, face arrest warrants for their alleged roles in efforts to buy the damaging information and Silva fired his campaign manager days before the election. The president has repeatedly denied knowledge of any wrongdoing.

Alckmin, of the centrist Social Democracy Party, voted Sunday in Sao Paulo’s upscale neighborhood of Morumbi. He said he was sure there would be a runoff election and that “ethics will defeat corruption.”

For many voters, the corruption allegations appeared to be a deciding factor.

“I’m not going to tell you who I voted for, because the vote is secret,” said Adelaide Venissato, a 53-year-old woman who owns a clothing store. “But I will tell you who I didn’t vote for. I didn’t vote for Lula. We expected so much and we got very little in terms of security and clean government.”