Brazilian legislators on Wednesday night chose an ally of President Luiz Inacio Lula da Silva to be the speaker of the lower house of Congress, relieving some of the political pressure on an administration dogged by campaign finance and vote-buying scandals.

Aldo Rebelo, a former minister in Lula's cabinet, narrowly defeated Jose Thomaz Nono, the interim speaker and a political opponent of Lula's. Rebelo is expected to steer the country's legislative agenda and lead the political corruption investigations that have targeted Lula's Workers' Party and forced the resignations of several high-ranking allies in public office.

"You could say it puts water on the fire but doesn't completely extinguish it," said Jose Luciano de Mattos Dias, a political scientist in Rio de Janeiro. "It doesn't change the dynamic of political crisis that still exists."

The vote came one week after extortion allegations forced Severino Cavalcanti, a legislator who is considered a Lula ally, to abandon the speaker's post. Besides influencing the flow of legislation in Congress, the new speaker will have the authority to approve or reject any attempts to impeach Lula.

Impeachment proceedings would have been unlikely even had Nono been chosen, according to analysts, because Lula has not been directly implicated in charges of vote-buying and campaign finance irregularities. Rebelo's election makes those chances slimmer, but it does not mean that Lula's administration will be able to reverse the political damage that has accompanied the crisis and paralyzed its legislative agenda.

"Aldo is certainly a government ally and is seen as a sort of precaution against a potential inflammation in the crisis," said analyst Rogerio Schmitt. "But the government has already lost control. Lula will finish his term and eventually try to get reelected, but nothing important will be voted on until then."

Lula lobbied hard this week for Rebelo, a former minister of political coordination and a member of the Communist Party. To win support for Rebelo among members of Nono's Liberal Front Party, Lula promised increased funding for the Transportation Ministry, which that party controls. Lula also blocked his own party from fielding a candidate, fearing it would take votes from Rebelo.

Cavalcanti's resignation was the latest stemming from corruption allegations that started in May with charges that members of the Workers' Party were paying other legislators for their support. Four senior officials in Lula's party were ousted for their roles in the scandal.

Lula's chief of staff, Jose Dirceu, resigned in June after it was alleged that he knew the party had used more than $24 million in undeclared loans to repay campaign debts. Then, this month, the top aide to Lula's finance minister resigned after allegations of kickbacks emerged.

A poll released last week by the Brazilian Institute of Public Opinion and Statistics showed that 49 percent of respondents disapprove of Lula's administration while 45 percent approve. Another poll by the organization showed that despite the setbacks, Lula remains the front-runner for the 2006 election.

Special correspondent Raquel Sacheto in Brasilia contributed to this report.

Aldo Rebelo, an ally of Brazilian President Luiz Inacio Lula da Silva, celebrates with colleagues after being elected lower house speaker.