Two recent polls showed da Silva's Workers Party would get about 63 per cent of the vote in the run-off vote on Sunday.
The same polls suggested that Geraldo Alckmin's Social Democratic Party would take about 37 per cent of the vote.
Da Silva's party has been hit for two years by charges of vote-buying and illegal campaign financing, scandals that have cost the former labour leader and lathe operator his aura as an ethical defender of left-wing political morality.
However, voters appear unwilling to abandon him for Alckmin, a former Sao Paulo governor, whose flat campaigning style and uncharismatic image have failed to win over working-class voters.
Man of peace
Silva wrapped up his campaign on Saturday in Sao Bernardo do Campo, the city where he first started working as a union leader, organising strikes and facing down the country's 1964 to 1985 military dictatorship.
At the rally, Silva told thousands of supporters he was already working to make peace with the opposition after a bruising campaign which saw Brazil sharply divided along class lines.
Silva said: "The political parties understand there is a time to fight and a time to govern the country. You know that I am a man of peace, I won't let the disagreements during the elections interfere with the way I govern."
More than 125 million Brazilians are expected to vote in Sunday's second round runoff elections for president and for governor in 10 of Brazil's 27 states where elections were not decided in the first round.
The voting will be carried out on electronic voting machines and the results are expected by 0100 GMT.
During a final campaign visit to Rio de Janeiro, Alckmin said he believed his performance in a debate with the president on Friday had paved the way for him to pull off a victory upset.
Alckmin said: "I feel the wave of an upset. The expectations are very good. The population is aware that Brazil needs to change and it is the vote that changes things."