Mexico City's mayor says he will be a candidate for the presidential nomination of the leftist Democratic Revolution Party.
Mayor Marcelo Ebrard is competing with Andres Manuel Lopez Obrador, who narrowly lost the 2006 presidential election.
Party leaders say they will commission an opinion poll of the general public to pick their nominee. Ebrard runs slightly ahead of Lopez Obrador among all voters, while Lopez Obrador is favored by party members.
Ebrard said Wednesday he is proposing "a fairer, safer and more prosperous society."
The front-runner in polls on the 2012 race is former Mexico State Gov. Enrique Pena Nieto. He announced this week that he will seek the nomination of the former ruling Institutional Revolutionary Party.