A leftist former military officer, Ollanta Humala, who promises to favour the poor by redistributing Peru's mineral wealth was expected to win the most votes in Sunday's presidential elections, but also to fall far short of the outright majority needed to avoid a runoff.
This has made the tight battle for second place crucial, as no other candidate has expressed any intention of seriously shaking up the economic status quo.
Technically tied for second in an election-eve poll were Keiko Fujimori, 35-year-old daughter of the imprisoned former President Alberto Fujimori, whom Peruvians alternately adore and vilify, and Pedro Pablo Kuczynski, a 72-year-old former World Bank economist and investment banker.
Trailing them was Alejandro Toledo, Peru's president from 2001-2006.
Polls opened Sunday morning at 9am (9am EDT; 01:00 GMT).
Front-runner Ollanta Humala, who has spooked foreign capital by promising a greater state role in the economy and exporting less natural gas while making it cheaper for Peruvians, prevailed in the first round of the 2006 presidential election only to lose a runoff.
This resource-rich, corruption-marred Andean nation has been noted for its volatile politics since the 1980s, when discredited political parties all but dissolved and elections became more about personality than ideology.
Sunday's vote — whose two top vote-getters will meet in a 5 June runoff — promises to be the most unpredictable in decades.
Humala was preferred by 28.1 per cent of voters in an Ipsos-Apoyo poll of 6,000 voters Saturday, followed by Fujimori with 21.1 per cent; Kuczynski with 19.9 per cent; and Toledo with 16.8 per cent. The poll had a margin of error of plus or minus 1.6 percentage points.
Peruvian law prohibits the publishing domestically of opinion polls in the campaign's final week.
Kuczynski, a German immigrant's son who was economy minister and prime minister under Toledo, climbed to be a contender from single digit showings in the poll in the campaign's final month, during which he renounced his dual US citizenship.
But his light skin color is a liability in a country where the European-descended economic elite is encountering a backlash of resentment from natives who have long been excluded from power.
Analysts say about 11 per cent of the electorate remain undecided and the electorate is even more fragmented than in 2006, when outgoing President Alan Garcia beat Humala, 53 per cent to 47 per cent.
Humala, 48, surged into the lead in the campaign's final days with populist promises of free nursery school and public education, state-funded school breakfasts and lunches, a big boost in the minimum wage and pensions for all, beginning at age 65.
Keiko Fujimori has made similar promises in this country of 30 million where one in three Peruvians lives on less than $3 a day and lacks running water.
But, unlike Humala, Fujimori is a free-market defender.
While Humala says he would respect international treaties and contracts (60 per cent of Peru's exports are from mining), many Peruvians don't believe him.
Humala advocates rewriting the constitution, just as Chavez and his leftist allies in Bolivia and Ecuador have done, to make it easier to enact his agenda. He says he does not, however, seek to include reelection, as Chavez did to stay in office.
Humala as an agent of change appeals to the lower classes, who make up a majority.
An economic boom from higher global commodity prices (Peru is a top exporter of copper, gold, silver and other metals) that has averaged seven per cent over the past five years simply hasn't trickled down to the poor.
Humala's biggest draw may be his anti-corruption stance — he wants to give voters the right to oust any elected official by recall. Last year, Peru was ranked 78th out of 178 countries in the global corruption index of Transparency International, tied with China and Serbia.
Fujimori has a rock-solid constituency thanks to her father's defeat of the Maoist-inspired Shining Path insurgency, taming of hyperinflation in the 1990s and delivering of basic services to long-neglected backwaters.
But Alberto Fujimori is now serving a 25-year sentence for corruption and authorising death squad killings, and his daughter's campaign and congressional slate are jammed with his former cabinet ministers and other loyalists. Foes contend he would call the shots from his comfortable prison cell, becoming the eminence grise behind a Keiko presidency.
Toledo, 65, squandered an early lead in the campaign, analysts say, by diluting his early message of greater economic justice, including a greater share of mining royalties for Peruvians.
Opinion polls show he would defeat Humala in a second round while Kuczynski and Fujimori would have a harder time against the "comandante."