UPDATE 3-Brazil's Rousseff extends lead over Silva in election poll
(Adds results of second poll)
By Anthony Boadle
BRASILIA, Sept 29 (Reuters) - President Dilma Rousseff's expected victory margin over closest rival Marina Silva has surged to 9 percentage points in a second-round runoff in Brazil's presidential election, an opinion poll showed on Monday, causing stocks and the real currency to tumble.
Rousseff would win the runoff with 47.7 percent of the votes against 38.7 percent for Silva, polling firm MDA said, widening her lead from the one-point advantage she had in the previous survey by the firm last week.
Another survey released later on Monday by the Vox Populi polling firm showed Rousseff with a seven-point lead over Silva in a runoff, unchanged from a week earlier.
Polls by MDA and Vox Populi are not as closely followed as surveys by the bigger research firms Datafolha and Ibope, which use larger samples of voters and conduct polls more frequently.
The first round of Brazil's presidential election is on Sunday. No candidate is expected to win more than 50 percent of the valid votes, which would trigger a runoff round between the top two vote-getters on Oct. 26.
The election is being closely watched by many investors who would like to see Silva, a popular environmentalist who has embraced pro-market policies, unseat leftist Rousseff and end 12 years of Workers' Party rule.
Some investors blame Rousseff's policies for the stagnation of Latin America's largest economy, and markets were weighed down by a Datafolha poll on Friday that was confirmed by Monday polls showing the incumbent consolidating her re-election chances. Continuación...