Updated

Brazil's top electoral court on Friday began debating whether jailed former President Luiz Inacio Lula da Silva — the campaign front-runner — will be able to run in October's presidential election or be barred due to a corruption conviction.

The first of the seven judges cast a vote against da Silva, but it wasn't clear if the full court would reach a decision before adjourning for the night.

The left-leaning da Silva, who was hugely popular when he left office in 2010, started serving a 12-year-sentence for corruption and money laundering in April. By law, the former president is barred from running since his conviction has already been upheld by one appeals court.

However the former president and his Workers' Party argue he should be able to run while he pursues further appeals.

Supreme Court Justice Luis Roberto Barroso said the decision to bar da Silva was "very simple" due to the conviction and later appeals court ruling.

He said the Workers' Party should replace da Silva in up to 10 days and said he should not appear as a presidential candidate in free airtime that is given to political parties on nationwide TV and radio starting on Saturday

Da Silva's lawyers complained the court was rushing a decision because they submitted their defense only on Thursday and noted that the court rarely holds sessions on Fridays.

If da Silva is barred, former Sao Paulo Mayor Fernando Haddad is seen as his likely candidate for the presidency.

Currently Haddad is candidate for vice president. Polls say the support for his bid as replacement is minimal so far, but da Silva's resilient popularity could boost the former mayor's hopes.