Polls give a slight edge to incumbent Dilma Rousseff, 66, who is seeking a second four-year term. Her Workers' Party has held power for 12 years and leveraged an economic boom to expand social welfare programs and lift over 40 million people from poverty.
But many voters believe Aecio Neves, a 54-year-old former state governor with strong support among upper-middle class and wealthy Brazilians, offers a much-needed change of the guard for Latin America's biggest economy. A decade of growth peaked at 7.5 percent in 2010 and has flagged since Rousseff took office.
Despite acrimonious finger pointing and corruption scandals that have characterized the campaign since a first-round vote on Oct. 5, voters are likely to be divided between those who feel better off than they did before the Workers' Party took office and those who believe its reign, no matter how successful, is no longer producing results.
"Forget the noise on both sides," said Alexandre Barros, a political consultant in Brasilia, the capital. "This is about an individual choice by each voter - what's in it for me?"
Rousseff has promised to deepen flagship welfare programs and seek to restore growth with a new economic team, Reuters reported.
Neves also vows to keep the social benefits while adopting more market-friendly fiscal measures to rein in public spending, take a tougher stance against inflation and give the central bank more autonomy to set monetary policy.
The choice takes Brazil back to a clash between classes in a country still riven by inequality.