Prosecutors ordered the arrest of a top media strategist for the governing Workers’ Party on Monday, on allegations that he received illegal offshore transfers from a firm suspected in the massive bribery scheme that has shaken the political establishment here.

João Santana, who advised the election campaigns of President Dilma Rousseff and her predecessor, Luiz Inácio Lula da Silva, was out of the country when police searched his home in the northeastern state of Bahia. After declaring in a statement that he had just quit work on a political campaign in the Dominican Republic, Santana was set to return to Brazil late Monday.

Prosecutors cited evidence that Santana had received $3 million from Odebrecht, Brazil’s largest construction firm, through a Panamanian shell company. Odebrecht allegedly skimmed the funds from contracts awarded by Petrobras, the state-controlled oil company, as part of a conspiracy to funnel billions of dollars in bribes to the Workers’ Party, its allies in Congress and other officials, according to prosecutors.

Santana’s attorney Fábio Toufic declined to comment, but the media strategist’s company has previously denied that it received undeclared funds. In a statement, Odebrecht said it is cooperating with investigators, declining to comment further.

The Petrobras scandal had lost steam in recent weeks as the outbreak of the mosquito-borne Zika virus captured headlines. After a year of political gridlock and economic recession, Rousseff appeared in a fresh role leading the efforts to fight the epidemic, which is suspected of causing birth defects in hundreds or thousands of babies.

For Rousseff, Monday’s operation raises the stakes in the wide-reaching corruption probe known as Lava Jato, or Car Wash, which erupted in the months leading up to her reelection in 2014. No evidence has implicated her directly, but she faces two separate proceedings that could lead to her ouster.

One, an impeachment case to be decided by Congress, focuses on whether Rousseff violated budget rules. The other, before Brazil’s electoral court, accuses her reelection campaign of taking bribes from the Petrobras scheme.

While the political will for impeachment has weakened, João Augusto de Castro Neves, a political analyst at the Eurasia Group consulting firm, says the arrest order for Santana increases the chances that the electoral court could invalidate her 2014 victory, causing new elections to be called.

“Today’s operation shows that the risk that the president will be removed from office is still reasonably high,” Neves said. “There’s not much she can do to react. The judiciary, police and prosecutors all enjoy a certain degree of autonomy.”

The Car Wash probe has little precedent in Brazil, where impunity has typically been the norm for the wealthy and powerful. A judge has handed down convictions for a former Workers’ Party treasurer and top executives at construction firms that were major campaign donors to governing and opposition parties.

Santana, 63, helped Lula win reelection in 2006. He also worked on the presidential campaigns of Venezuela’s Hugo Chávez and his successor, Nicolás Maduro, and for the campaigns of presidents in El Salvador, Angola and, most recently, the Dominican Republic.

In a document made public as part of Monday’s operation, police cited notes said to be from Marcelo Odebrecht, the former head of the construction giant, suggesting that his company covered about $3 million in construction costs for the headquarters of Lula’s foundation. It is one more indication that Lula — who left office in 2011 as the most popular president in Brazil’s history — may have received favors from construction firms that won lucrative government contracts and subsidized loans.

Last year, prosecutors began investigating whether Lula had engaged in influence peddling by giving paid speeches abroad for Odebrecht and promoting the company with foreign leaders. If confirmed, the allegations could change the face of politics in Brazil. Lula remains a power broker and political mentor to Rousseff, his handpicked successor, and many speculate he could run for the presidency again in 2018.

Lula’s foundation, Instituto Lula, has previously denied allegations of influence peddling and said that its headquarters was acquired in 1991. Rousseff’s office declined to comment on Monday’s operation.

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