(Adds new opinion poll numbers)
By Anthony Boadle
BRASILIA, Sept 5 (Reuters) - Brazil's front-running far-right presidential candidate Jair Bolsonaro rallied supporters on Wednesday with a message of a clean break from the past as a new opinion poll showed him consolidating his support among voters fed up with rampant corruption.
Charges filed against two of his main rivals in recent days could further strengthen his presidential bid.
Bolsonaro, a former army captain, is running on an anti-graft, law-and-order campaign. He labels his opponents from the Workers Party (PT) and the Brazilian Social Democracy Party (PSDB) as criminals who took part in corruption.
"We're going to sweep the leaders of these parties into the dustbin of history," Bolsonaro told several thousand backers at a rally in a working class suburb of Brasilia. "Brazil cannot stand another government by the PT or PSDB."
Bolsonaro then kicked into the crowd an inflatable doll portraying jailed former president and PT founder Luiz Inacio Lula da Silva. Lula, who easily leads opinion polls, is banned from running because of a graft conviction.
A poll by Ibope showed Bolsonaro increasing his lead by two percentage points to 22 percent for the Oct. 7 first-round vote, though he would lose to most rivals in a likely runoff ballot. Environmentalist Marina Silva and center-left populist Ciro Gomes are tied at 12 percent.
PSDB candidate Geraldo Alckmin and PT presidential contender Fernando Haddad, whose parties have governed Brazil for 21 of the last 23 years, are struggling to gain traction and are in the single digits. Both have had corruption charges filed against them this week, which they deny.
Congressional deputy Major Olimpio, a campaign manager for Bolsonaro in Sao Paulo, said those charges "exposed what is obvious" and reinforced Bolsonaro as the clean candidate.
Bolsonaro is trying to win over roughly one-third of voters who tell pollsters they will nullify their ballots or not vote for anyone, highly disillusioned with politics-as-usual after years of investigations that exposed stunning levels of graft.
Major Emilio Kerber, a shaven-head active duty Air Force officer who is running for Congress, said that Bolsonaro "represents the anger of Brazilians with political corruption."
"He is the only candidate who can break clean with the traditional give-and-take politics that we are tired of," Kerber said at Wednesday's rally.
Bolsonaro is facing charges of his own of inciting hate and rape. He says he has done nothing wrong and the charges are politically motivated.
Earlier on Wednesday, Brazilian state prosecutors accused Alckmin of taking 10 million reais ($2.4 million) in illegal campaign funding. The charges are civil and not criminal, and must be accepted by a judge before going to trial.
Alckmin's campaign denied any wrongdoing by the candidate and accused the prosecutors of having political motivations as they filed charges just a month ahead of the election.
Prosecutors accuse Alckmin of taking campaign funds from Odebrecht SA, a scandal-plagued construction conglomerate, when he was running for governor of Sao Paulo state in 2010 and again in 2014.
The charges are unlikely to halt Alckmin's campaign. Under Brazilian law, a politician can only be barred from running if convicted of a crime that is upheld on appeal, which cannot possibly occur before next month's vote.
On Tuesday, the PT's Haddad was charged by state prosecutors in Sao Paulo with corruption, charges he denied. The charges must be accepted by a judge to go to trial.
$1 = 4.1618 reais Reporting by Anthony Boadle Additional reporting by Pedro Fonseca in Rio de Janeiro and Eduardo Simoes in Sao Paulo Writing by Brad Brooks Editing by Rosalba O'Brien and Grant McCool