Jose Serra prepared on Friday to step down as governor of Sao Paulo state at midnight to run for Brazil's presidency as the main opposition candidate in October elections.

The 68-year-old Serra, a well-known former health minister who is expected to be confirmed as the candidate of the centrist PSDB party, leads opinion polls in the race to succeed President Luiz Inacio Lula da Silva.

Lula's chosen candidate, Dilma Rousseff of the center-left ruling Workers' Party, is running second and has closed the gap on Serra in recent weeks.

Serra, who lost to Lula in the 2002 presidential race, is expected to be confirmed as the PSDB candidate on April 10. Public officials are required by law to step down by April 3 if they want to run in the Oct. 3 election.

Despite Serra's lead in polls, most analysts make Rousseff the favorite because she can count on support from the hugely popular Lula and will be helped by the rebounding economy.

Serra is likely to tout his executive experience as governor of Brazil's financial center and most populous state in his appeal to voters. He is also seen as more in favor of private investment and a smaller role for the state than former leftist militant Rousseff.

But both Rousseff and Serra believe in a strong government role in the economy and are unlikely to mark a major change in the policies that have helped Brazil's economy stabilize and grow strongly under Lula.

Reuters