Rousseff has vowed to continue the market-friendly policies of the outgoing president [Reuters]

Dilma Rousseff, the ruling party candidate in Brazil's presidential race, has taken the lead after more than 90 per cent of ballots counted but may be denied a first-round victory.

The endorsed candidate from outgoing president Luiz Inacio Lula da Silva's Workers' Party is ahead of her closest rival by 12 points after securing 46 per cent of valid votes.

She is likely to face her nearest rival, Jose Serra, the opposition candidate and former Sao Paulo state governor, who garnered 33 per cent of the votes.

Rousseff, a former Marxist guerrilla and Lula da Silva's former chief of staff,  is favoured to beat Serra in the next round and become the first woman to lead Brazil.

Serra, one of Brazil's most experienced politicians, should now have an additional four weeks to chip away at Rousseff's lead.

If the election does go to a second ballot, it could be due to spoiler candidate Marina Silva, a former environment minister who is not related to the president. Silva had about 20 per cent of valid votes.

Runoffs are common in Brazil – Lula faced them in 2002 and 2006, and emerged with a strong mandate in both cases – and Rousseff is expected to take victory.

Influential leader

Lula has dominated the campaign despite being barred by the constitution from running for a third consecutive term.

Rousseff joined the outgoing president in his hometown of Sao Bernardo do Campo on Sao Paulo's southern outskirts for a large rally on Saturday ahead of the election.

The president enjoys an 80 per cent popularity rating - unprecedented in Brazilian politics - and many voters are prepared to support Rousseff due to his endorsement. For her part, Rousseff has pledged to continue many of her mentor's investor-friendly policies.

Lucia Newman, Al Jazeera's Latin America editor, reporting from Sao Paulo, said that the main change in Brazil after the election was likely to be the gender of the president.

"[Rousseff] is very much the candidate of continuity. She is promising no more, no less, than President Lula's economic, social and foreign policies," she said.

Candidates' achievements

Serra, right, has struggled to close on Rousseff and is polling at about 31 per cent [Reuters]

While none of the three leading candidates come close to mustering the magnetic charisma President Silva has, they all have histories just as fascinating as his.

Rousseff was a key player in an armed militant group that resisted Brazil's 1964-85 military dictatorship.

She was imprisoned for nearly three years beginning in 1970 and tortured. She is a cancer survivor, a former minister of energy and chief of staff to Silva.

She is more moderate than in her youth and has promised a government of pragmatic capitalism.

Serra, in addition to being a former mayor and senator, served as health minister under President Fernando Henrique Cardoso and won praise for defying the pharmaceutical lobby to market inexpensive generic drugs and free anti-AIDS medicine.

Marina Silva, 52, is a renowned environmentalist who was born in the Amazon, the daughter of a poor rubber tapper. Despite being illiterate into her teens, she went on to earn a university degree and has since worked tirelessly to defend Brazil's rain forest.

About 135 million voters also cast ballots for governors, mayors and state and federal houses of Congress. Under Brazilian law, voting is mandatory for citizens between the ages of 18 and 70. Not voting could result in a small fine and make it impossible to obtain a passport or a government job, among other penalties.

Electoral authorities in Brasilia said 368 people were arrested across Brazil on Sunday for election violations, such as trying to buy votes, illegally transporting people to polls and distributing campaign materials past deadline.

Source: Al Jazeera and agencies