The Brazilian government's economic policies have been a particular bugbear for investors, who have turned their back on the country in recent months, but a number are now increasing their exposure in the expectation there may be a rally if the voters deliver a surprise.
While President Dilma Rousseff started the year as the favourite for winning the election, her popularity has since slid. In the wake of the World Cup, her approval ratings have dropped from 38% to 34%, according to a recent Ibope poll.
The presidential race suffered a further upset when opposition candidate Eduardo Campos died in a plane crash this month. His replacement, Marina Silva, has 29% of voter support since she stepped up to lead the campaign.
ING Investment Management senior emerging market strategist Maarten-Jan Bakkum believes Silva has a potent combination of charisma and an astute economic agenda, which could win voters over.
I personally think Silva will be the next president
He said: "The plane accident a few weeks ago completely changed the dynamic of the election. The chances of a Rousseff victory have decreased. I personally think Silva will be the next president.
"Brazil is a weak story, but there is potential for change. It is a bit of a binary call, because if the opposition does not win there is probably downside."
The MSCI Brazil index has returned -9.29% in the three years to 10 September 2014. However, in the last six months, the index returned 33%, as investors hold out hope a new regime could power the economy.
Silva, who represents the centre-left Brazil Socialist Party, is not the only politician mounting a serious challenge to Rousseff. Centrist Aécio Neves has a 19% approval rating, according to the Ibope poll, although this has dropped from earlier measurements.
Hermes Global Emerging Markets head Gary Greenberg compared Silva to Lula, the popular ex-president from Rousseff's family.
He said she combined this charisma with a reformist economic agenda: "This attractive combination is what drew not only ‘undecided' voters to vote for her but also [Rousseff's party] PT supporters that want to continue spending on social programmes but with more prudent fiscal management."
Silva has a decent chance of making it to the second round against Rousseff, he added: "Even if Neves makes the second round instead of her, we expect her voters will vote for Neves as ‘anyone but Dilma' sentiment has gained traction as a theme.
"Thus there is now a good chance that Rousseff will not win the elections, which we believe would be positive for the Brazilian market."
Though he remains positive on the country, Greenberg cautioned the current rally may cool whatever the result on 5 October.
"Even if [Silva] wins the market may come back a little. It is on the verge of discounting more than she can deliver," he said.
