Mexico will decide whether to join the growing leftist camp in Latin America or stick with a free-market path in a presidential election on Sunday that is balanced on a knife-edge.
In a country crucial to US interests in border security, trade and immigration, polls show an extremely close race between leftist anti-poverty crusader and former Mexico City Mayor Andres Manuel Lopez Obrador and conservative Felipe Calderon, a former energy minister from the ruling party.
Lopez Obrador, 52, leads opinion polls by about only 2 percentage points after almost six months of bruising campaigning that split a country still finding its feet with full democracy after seven decades of one-party rule ended in 2000.
The leftist, who rejects any comparisons to US foe Venezuelan President Hugo Chavez, promises to slash bureaucracy to pay for welfare programs he says will lift millions out of poverty.
Supporters of Calderon, 43, accuse Lopez Obrador of populism and say he would overspend and mire Mexico in debt.
"He is a danger for Mexico. He promises everything to everyone without explaining how he is going to pay for it," said waiter Hector Morgan, 20.
Another candidate, Roberto Madrazo, lags in third place but his once long-ruling Institutional Revolutionary Party, or PRI, has an electoral machinery famed for getting its supporters out to vote and he may do better than his poll numbers suggest.
Turnout is expected to be reasonably high, at about two-thirds of Mexico's 71 million voters, after polling stations open.
Voting ends 12 hours later and official results are expected earlt tomorrow morning.
In a country where at least half the population lives on less than $5 a day, Lopez Obrador has won support by promising to give pensions to those over 70 and cut energy prices.
His supporters complain that President Vicente Fox's National Action Party, or PAN, failed to live up to promises to create jobs and alleviate poverty, even though Mexico has one of the region's most stable economies.
Mr Fox cannot run for office again under Mexican law. Financial markets are hoping for a Calderon victory but worry that Lopez Obrador, a former Indian welfare officer with a history of organizing protests, might not accept that result.
Mr Lopez Obrador is expected to launch a legal challenge and maybe even street demonstrations if he loses by a narrow margin and suspects fraud. There is no runoff in Mexico, so whoever gains the most votes wins the election. The United States has kept on the sidelines of the campaign, not even hinting at support for any candidate, but Calderon is more in line with US views on politics and business.
He would seek foreign investment in energy. Lopez Obrador says his fight against poverty would curb illegal immigration to the United States, which has become a major political issue in that country, by giving Mexicans more reason to stay home. Sunday's winner will also inherit a fight with drug cartels, which have carried out a wave of beheadings in the past week.
Voters will also choose federal deputies and senators and with the country split three ways, the next president is unlikely to have a majority in Congress.