Mexico's presidential candidates have hurled accusations at each other and at an empty podium left vacant by the race's fading front-runner during a televised debate in the capital.

Andres Manuel Lopez Obrador, the leftist Democratic Revolution Party candidate and former mayor of Mexico City, had announced weeks ago that he would not attend the first of two debates ahead of the July 2 presidential election.

Felipe Calderon of the ruling conservative party (National Action Party) attacked Lopez Obrador in his absence Tuesday. He said the politician was not there because he had nothing to offer voters.

Calderon, who gained the lead in a closely-watched opinion poll this week, laid out his plan to lift Mexico out of poverty.

He also traded criticisms with the third main candidate, Roberto Madrazo, of the Institutional Revolutionary Party.

Some information for this report was provided by AP and Reuters.