Paulo Roberto Costa was living an oilman’s dream. He had a house in a luxurious gated community here. He bought a yacht and drove an armored Range Rover. He had more than $25 million stashed in bank accounts in Switzerland and the Cayman Islands. But that dream evaporated recently when the police arrested Mr. Costa and charged him with orchestrating a bribery scheme on an epic scale at Petrobras, Brazil ’s national oil company, and funneling the proceeds to the governing Workers Party and its allies while enriching himself. The case has presented a major challenge to President Dilma Rousseff , who is in a bitter re-election fight against Aécio Neves, a centrist who has been gaining momentum as the vote next Sunday approaches. With the two candidates battling each other for the lead in opinion polls, Mr. Neves is seizing on the oil scandal […]