Preferred shares of Brazilian state oil company Petrobras rose sharply on Friday as investors bet that President Dilma Rousseff will not be able to win re-election in the first round of the October elections. The death of the presidential candidate Eduardo Campos in a plane crash on Wednesday raised expectations that their popular running mate Marina Silva is the representative of his party in the elections, complicating Rousseff's aspirations of winning without having to go to a second round . Investors expect a new government to approve more favorable to the interests of the minority shareholders of Petrobras policy. Some analysts said the market reaction may have been exaggerated by the term of stock options contract on Monday.