Former Brazilian President Luiz Inacio Lula da Silva attends the celebrations of the 38th anniversary of founding the Workers' Party in Sao Paulo, Brazil February 22, 2018. REUTERS/Paulo Whitaker

SAO PAULO/BRASILIA (Reuters) - Former Brazilian President Luiz Inacio Lula da Silva would easily win a second-round runoff vote against several likely opponents and retake the presidency in October elections if allowed to run, according to a poll released on Tuesday.

Lula, who is likely to be barred from running because of a corruption conviction that was upheld on appeal in January, also had the lowest rejection rate among likely contenders in the survey, conducted by pollster MDA. Support for him in several potential second-round matchups rose from levels in an MDA poll in September.

Still, nearly half of those polled, 46.7 percent, said they would never vote for Lula, underlining widespread voter discontent with political choices in Brazil as graft investigations continue to target the political class.

In a runoff vote against right-wing congressman Jair Bolsonaro, the MDA polls found, Lula would take 44 percent of the vote against 26 percent for his opponent.

If Lula is barred by courts from running for the presidency, the poll found that Bolsonaro would face environmentalist and former senator Marina Silva in a second-round runoff, which takes place in Brazil if no single candidate wins a majority of votes on the first ballot.

Bolsonaro and Marina Silva are polling within the survey’s margin of error in a theoretical runoff, MDA found, a situation repeated in other likely second-round scenarios absent Lula.

Lula has said repeatedly that he wants to run and will fight for that chance in Brazil’s top courts. However, the country’s constitution, with rare exceptions, bans politicians from running for office if their convictions have been upheld on appeal. The question of whether Lula can run is not likely to be settled by the courts for several months.

The survey showed that the vast majority of those asked think President Michel Temer is doing a poor job as president, with 73 percent giving a negative evaluation, little changed from the last poll in September, when Temer received a negative rating from 76 percent.

The MDA poll, which had a margin of error of 2.2 percentage points, was commissioned by national transportation association CNT and surveyed 2,002 people across Brazil from Feb. 28 to March 4.