By Dave Graham

 

MEXICO CITY (Reuters) - Mexican presidential front-runner Andres Manuel Lopez Obrador faces a test of his mettle on Sunday night as he squares off against rivals in the first televised debate of the campaign for the July 1 election.

 

The veteran leftist has built up a commanding lead in opinion polls since the campaign formally began at the end of March, with one voter survey in the past week putting the former Mexico City mayor 22 points ahead of his nearest challenger.

 

That could make the 64-year-old Lopez Obrador the principal focus of attack in the debate among five candidates, with his competitors running out of time to make up ground.

 

So far, his two main rivals, Ricardo Anaya, who leads a right-left alliance, and Jose Antonio Meade, candidate of the ruling centrist Institutional Revolutionary Party (PRI), have devoted much of their energy to battling each other for second.

Lopez Obrador came within a whisker of winning the presidency in 2006 and was runner-up again six years later.

Buoyed by widespread discontent with the PRI over corruption, record levels of violence and sluggish growth, he has never approached the final two months so far ahead.

This time, Lopez Obrador has cut a more relaxed figure on the campaign trail, generally avoiding the kind of outbursts that in the past helped adversaries depict him as a radical menace to stability in Latin America's No. 2 economy.

He has moderated much of his economic rhetoric, although his threats to scrap a $13 billion Mexico City airport now under construction have dismayed many influential business leaders.

Anaya, 39, is polling second in most surveys, but he has struggled to extricate himself from a mud fight with the PRI, which has tried to discredit him with corruption allegations over a 2014-2016 property deal in his home state of Queretaro.

He dismisses the accusations, but the dispute has dented his momentum and supporters believe he must take risks in the debate, which starts at 8 p.m. (0100 GMT Monday).

"It's tough for Anaya, he's got to make a splash," said his ally Fernando Belaunzaran, a former congressman for the center-left Party of the Democratic Revolution. "But this could be a turning point, because after the debate it may be beyond doubt that it's a two-horse race between Andres Manuel and Anaya."

(Reporting by Dave Graham; Editing by Peter Cooney)