Mexican presidential front-runner Andres Manuel Lopez Obrador faces a test of his mettle yesterday 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.