It's a nail-biter of an election -- and polls show Brazilian President Dilma Rousseff has clawed her way back into the lead.

She cast her ballet, Sunday, as more than 140 million registered voters head to the polls.

Her main competition -- Marina Silva who was thrust into the spotlight after Brazil's Socialist Party's original candidate was killed in a plane crash.

She tapped into the anti-establishment mood on the streets -- one that saw mass protests erupt over employment laws, health and education.

Just behind Silva, is Aecio Neves -- a senator and former state governor from the centrist party, running on a pro-business platform.

Both Silva and Neves want reforms to the tax system -- to lower the cost of doing business in Brazil.

But do they have enough support to unseat Rousseff, who is highly popular with the working class?

Despite a weak economy, unemployment remains near a record low... and this, could be enough to swing voters her way.