Mexico's presidential election is too close to call with a leftist anti-poverty campaigner and the conservative ruling party candidate running neck and neck, exit polls said on Sunday.

The extremely close vote raised fears of a political crisis if any of the main candidates challenge the results and call street protests.

Two leading newspaper exit polls said Felipe Calderon of the ruling party and Andres Manuel Lopez Obrador, the left-wing former mayor of Mexico City, were locked in such a tight battle that it was impossible to declare a winner.

One exit poll from GEA-ISA said Calderon had a lead of 4 percentage points over Lopez Obrador, although it is not one of the most closely-watched polling firms and its pre-election polls never had Calderon trailing even when all others did.

The Federal Electoral Institute was expected to announce official results at around 11 PM (04:00 GMT on Monday).

If it is unable to call a winner, Mexico could face days or weeks of legal wrangling and protests similar to the fight that followed the US presidential election in 2000.

That would spook Mexico's financial markets, which are already nervous about Lopez Obrador's economic policies.

TV exit polls also said they could not call the race, but did not identify which candidates were locked in a tie.

Others, however, said Roberto Madrazo of the Institutional Revolutionary Party, which ruled Mexico for 71 years before it was toppled at the last presidential election in 2000 was trailing in third place. Madrazo aides rejected the poll results and said they were waiting for official returns.

Lopez Obrador won voter support with promises to end two decades of free-market reforms and pull millions out of poverty with welfare benefits and new jobs in ambitious infrastructure projects.

"Lopez Obrador is the only one who can bring a new Mexican revolution where the poor are the ones who win," said Amalia Rodriguez, a 19-year-old student in Mexico City.

Lopez Obrador was the red-hot favorite for most of the campaign but Calderon closed the gap with aggressive TV ads painting his rival as a danger to Mexico's economic stability and linking him to Venezuela's anti-US firebrand President Hugo Chavez.

It was a strategy that worked with many voters.

"Lopez Obrador is not a danger to Mexico; he's the enemy of Mexico," said Carolina Ocampo, a 34-year-old sunglasses saleswoman as after voting in Mexico City on Sunday.

Calderon, a stiff Harvard-educated lawyer and economist, has promised to create millions of jobs with pro-business reforms, more foreign investment and a boom in construction and house building.

He also vows to clamp down on violent criminals, from kidnappers to drug smugglers who have killed around 1,000 people in vicious turf wars so far this year.

President Vicente Fox took office after that historic victory pledging fast and far-reaching reforms. Hopes ran high but Fox failed to deliver on his promises of rapid economic growth and millions of new jobs, and opposition parties in Congress blocked his economic reform program.

He was barred under Mexico's constitution from seeking reelection.

(Chinadaily.com via agencies July 3, 2006)