A first round election victory may no longer be a sure thing for the governing party in Brazil.
A corruption scandal at its very heart has prompted many to ask whether Dilma Roussef, the prime candidate for the popular Worker’s Party, will win outright on Sunday – or be forced into a run-off.
Rousseff is still widely expected to become Brazil’s next President and its first female leader.
But whether that happens now or in a month’s time will have important implications for policy.
Handpicked as successor by the hugely popular Lula, Roussef is still more than 20 points ahead of her closest rival.
But the electorate in the world’s eighth largest economy was shocked when a close aide resigned after being implicated in a sleaze inquiry.
The corruption case is a gift for the opposition.
Rousseff’s leading opponent, José Serra, has sought to link her with the scandal, saying she was either complicit in the wrongdoing or else ignorantly unaware.
Whatever the effect on Sunday’s poll, political analysts say it is unlikely to significantly influence Brazil’s trajectory.
Lula’s eight years in office have resulted in low inflation, strong economic growth and millions of Brazilians being lifted out of poverty.