Jair Bolsonaro, far-right lawmaker and presidential candidate of the Social Liberal Party (PSL), gestures at a polling station in Rio de Janeiro, Brazil October 28, 2018.
Jair Bolsonaro, far-right lawmaker and presidential candidate of the Social Liberal Party (PSL), gestures at a polling station in Rio de Janeiro, Brazil October 28, 2018. Reuters / Pilar Olivares

Supporters of Brazilian President Jair Bolsonaro began pouring into a stadium in Rio de Janeiro on Sunday where they are expected to officially nominate the right-wing leader as a candidate for re-election in what has proven to be one of Latin America's bitterest political contests in years.

The right-wing Liberal Party (PL) is expected to tap Bolsonaro as their nominee for the Oct. 2 vote before an audience of roughly 10,000 in Rio's Maracanazinho, a move considered the official beginning of Bolsonaro's candidacy under Brazilian law.

The nomination comes as the president continues to launch baseless attacks on the reliability of the nation's electronic voting system, casting doubt on whether he would accept defeat.

That seems an increasingly likely possibility as Bolsonaro struggles to gain traction with voters, as high inflation continues to batter his image.

Some polls have the former army captain down almost 20 percentage points to former President Luiz Inacio Lula da Silva, who governed the nation from 2003 through 2010 and lifted millions out of poverty thanks to aggressive social spending during a period of rapid commodity-driven growth.

His star has fallen in recent years due to high-level corruption probes - Lula himself spent over a year and a half in jail due to a graft conviction that was later overturned - but he remains a relatively popular figure among Brazilians.

For Bolsonaro fans here, however, waving Brazilian flags and bedecked in the national soccer jersey, the possibility of a Lula comeback is unconscionable.

Vera Carvalho, 59, a Rio schoolteacher, said she hoped there would not be a coup, but if there were, it would be the fault of the left for attempting to install a corrupt president.

"I hope there isn't one, but I fear that there could be," she said. "Lula needs to go back to jail. He is vermin."

Inside, the stadium, which was about half full as Bolsonaro's speech approached, announcers jeered up the crowd and lawmakers snapped selfies with fans. A campaign jingle described the president as "the captain of the people."

At the convention, Bolsonaro is expected to focus on his government's achievements in ensuring religious and economic freedom, including his efforts to loosen gun ownership laws, according to campaign sources consulted by Reuters.

The leftist Workers' Party (PT) officially nominated Lula on Thursday, while left-of-center candidate Ciro Gomes, running in a distant third, was nominated by the Democratic Labor Party (PDT) on Wednesday.

In the coming weeks, the already tense battle between the top two candidates should heat up even further. In mid-August, Lula and Bolsonaro will be freed up by authorities to engage in most forms of political advertising.