July 29 (Bloomberg) -- Former Mexico City Mayor Andres Manuel Lopez Obrador, opening his campaign for the nation's presidency, pledged to make government assistance to the poor his top priority.

Lopez Obrador, speaking to thousands of supporters at the national auditorium in Mexico City, defended his work as mayor, highlighting public spending projects and his efforts to make the city safer.

``The most important aspect of my time as mayor, what fills me with the most pride, was to implement the principle that, for the good of everyone, the poor come first,'' he said. Lopez Obrador, 51, stepped down as mayor of Mexico City this week to seek Mexico's presidency.

Lopez Obrador led other likely candidates entering the 2006 presidential race in a nationwide poll taking between July 22-23 by Mexico's Institute of Marketing and Opinion. Forty two percent of respondents said they would vote for Lopez Obrador if the elections were held today, versus 27 percent who said they would vote for Santiago Creel of President Vicente Fox's National Action Party. Twenty percent favored Roberto Madrazo of the Institutional Revolutionary Party. The poll of 1,489 residents has a margin of error plus or minus 3 percent.

Earlier this month the former mayor outlined projects he would pursue as president including a new airport, revamping the nation's highways and building a bullet train to the United States.

Limitations

Lopez Obrador must overcome the limitations of his Party of the Democratic Revolution to win the presidency, said James Wilkie, a professor of history at the University of California at Los Angeles and president of the Worldwide Network for Mexico Policy Research. Unlike Madrazo and the Institutional Revolutionary Party, Lopez Obrador's party lacks resources to organize voters outside of Mexico City.

''Lopez Obrador has a long way to go and no base to get him there,'' Wilkie said.

In his speech today, Lopez Obrador said Mexico City's government during his term spent about $6 billion on social programs, including $944 million on low-income housing. ``This marks the most important investment in human well-being in the history of Mexico City, Lopez Obrador said.

The former mayor, who yesterday inaugurated improvements to Mexico City's center at the side of Carlos Slim, the world's fourth-richest man according to Forbes magazine, defended his support of private investment.

`Obstacles'

``No business person has encountered obstacles when trying to invest in the city,'' Lopez Obrador said. ``There was only no room for traffickers of influence and those used to prospering under the protection of government power.''

Lopez Obrador also said that homicide and robbery had declined during his administration, countering assertions by leaders of private groups such as Mexico United Against Crime who assert he did little to make the city safer.

Lopez Obrador supporters who gathered for his speech said he cared for the poor more than other candidates. ``He has helped the people by giving them money, said Javier Lopez,'' who sold bags of peanuts outside of the auditorium for 20 cents each.

To contact the reporter on this story: Patrick Harrington in Mexico City at pharrington8@bloomberg.net

Last Updated: July 29, 2005 17:07 EDT