Silva’s entry into the contest as a replacement for Eduardo Campos, who died in an Aug. 13 plane crash, has upended the race, with polls showing her attracting previously undecided voters.

Her pledges to slow inflation, grant central bank autonomy and check rising spending that led the country’s debt rating to be cut appeal to the mainly affluent supporters of rival Neves, while her personal story as a former maid appeals to poorer voters, said Rafael Cortez, a political analyst at research company Tendencias Consultoria Integrada.

Silva criticized Rousseff’s management of the economy in an Aug. 20 news conference. Her economic adviser, Eduardo Giannetti, said the previous day that policies to contain energy prices are “extremely harmful” in the short term.

Biggest Return
Silva would win in a run-off against Rousseff with 47 percent of the vote, compared with 43 percent for the incumbent, according to a Datafolha poll published Aug. 18. Rousseff’s 36 percent lead in the poll for the first round of balloting, compared with 21 percent for Silva and 20 percent for Neves, wouldn’t be enough to ensure a victory. To win in the first round a candidate needs more votes than the other competitors combined.

Petrobras returned 62 percent in dollar terms in the past six months, the biggest gain among the 20 most valuable oil producers. The average gain over the same span was about 15 percent.

Investors betting Petrobras will surge if Rousseff is voted out of office in October elections have a large chance of losing their money even if the she is defeated, said Robbert van Batenburg, director of market strategy at broker-dealer Newedge USA LLC.

They had better wait for evidence a challenger would swiftly phase out Rousseff’s expensive fuel subsidies to improve profitability at the most-indebted publicly traded oil company, Batenburg said in a phone interview from New York.

Eoin Treacy's view

The Brazilian market was in need of a catalyst to reignite investor interest following the collapse of mining company OGX, the disappointing performance of iron-ore, the massive capital raising of Petrobras and what many see as inept political leadership amid failure to promote growth and control inflation.

The failure of the Brazilian football team at this summer’s World Cup might appear trivial but many Brazilians appear to have seen it is as symptomatic of the issues facing the country and are increasingly likely to vote for change. Whether a new administration decides to remove the fuel subsidy is an uncertainty but they would be more likely to do so than Rousseff.

The Bovespa Index has broken a three-year progression of lower rally highs and continues to extend the advance.

Petrobras is also extending its rally having broken an even lengthier progression of lower rally highs.

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