By Lisandra Paraguassu and Maria Carolina Marcello
SAO PAULO (Reuters) -Brazilian business leaders, intellectuals and artists gathered on Thursday to read manifestos defending democratic institutions after attacks by President Jair Bolsonaro that have raised fears he could reject the results of October's presidential election.
The far-right leader and former army captain has questioned Brazil's electronic voting system and attacked Supreme Court justices who oversee elections, accusing them without evidence of favoring his leftist rival, who leads in opinion polls.
Prominent Brazilians, from top bankers to union leaders, signed a manifesto organized by Sao Paulo's confederation of industries (FIESP) expressing support for the judiciary as it prepares for the Oct. 2 election under fire from Bolsonaro.
They called the top court "the ultimate guardian of the Constitution" and said the Superior Electoral Court (TSE) has conducted the country's elections with total integrity.
Another manifesto, also read out to a cheering crowd at University of Sao Paulo's law school and signed by nearly a million people, warned that the country's democracy was under threat.
"Out with Bolsonaro," the audience shouted after the manifesto called "Letter to the Brazilians" was read in the same place as a similar manifesto was read in 1977 to denounce Brazil's military dictatorship at the time.
The manifesto was signed by former President Luiz Inacio Lula da Silva, who is the frontrunner in the presidential race, although his advantage has narrowed in recent polls.
Bolsonaro, an admirer of former U.S. President Donald Trump who backed his false claims of fraud in the 2020 election, ridiculed the manifesto, saying he had no need to sign a letter to prove his democratic credentials.
His opponents say he is preparing the ground to contest the election results if he loses, as Trump has done since 2020.
Several thousand demonstrators later marched along Sao Paulo's Paulista Avenue in support of democracy and chanting calls for Bolsonaro to stop threatening the voting system.
Similar demonstrations were planned by civil society organizations in other Brazilian cities.
"The purpose of the demonstrations is the defense of democracy ... against the threat of a coup," one of their organizers, Raimundo Bonfim, told Reuters.
Brazil's most polarized election in decades is expected to go to a second-round runoff between Bolsonaro and Lula on Oct. 30 if neither candidate win 50% of valid votes on Oct. 2.
The country's top newspapers canceled a presidential debate planned for Sept. 14 after the two main candidates did not confirm their participation. Bolsonaro said he would only debate after the first round. Lula cited scheduling difficulties.