But in the three latest polls, Fujimori only registered 18-22 percent of the vote. This left her trailing Lima mayor Luis Castaneda (19-22 percent) and some distance behind Toledo, who was top with a 25-27 percent range.

The field of three will be narrowed to two for the second round of voting in June.

Current President Alan Garcia cannot legally run for a third term, while his ruling APRA party's official candidate Mercedes Araoz withdrew from the race on Sunday with desperately low ratings.

Supporters had high hopes for Fujimori when she announced her candidacy in December at a rally for her Fuerza 2011 party in one of Lima's poorest neighborhoods.

"If I'm elected president, I won't be working out of the government palace, but from the country's poorest communities that I'll be visiting," said the young lawmaker.

Toledo, president from 2001-2006, announced his candidacy in November, and has seen steadily growing support.

An economist by training, the 64-year-old was elected after Fujimori's 1990-2000 regime collapsed amid a massive corruption scandal.

As president, Toledo had low approval ratings -- sinking once to below 10 percent -- in part due to a series of personal scandals.

However the country's economy has since boomed, and he has been credited with setting the groundwork for the continued growth seen under Garcia.

For the first time in years, noted US political scientist Steven Levitsky, none of the leading candidates are outwardly "anti-establishment" or railing against the liberal economic model.

The South American nation is currently riding a boom in mining amid a sharp 8.7-percent growth in its economy in 2010.

If elected, Fujimori would scrape by on eligibility, barely reaching the age of 36 required to become president. The eldest of four children, she was voted into Congress in a landslide in 2006.

Alberto Fujimori was sentenced in April to 25 years in prison on charges linked to running a secret army hit squad that killed 25 civilians during the country's brutal internal insurgency.

Keiko Fujimori has vowed to pardon her father and release him from jail if elected.