The presidential debate staged by Mexico's "Yo soy 132" student movement was plagued by transmission problems and the absence of frontrunner Enrique Peña Nieto, of the Institutional Revolutionary Party, or PRI.

The signal froze and resumed several times during the live streaming of the debate Wednesday on YouTube as about 90,000 people watched on that Web site and others followed the debate on various media Web sites.

The three candidates who took part in the closed-door debate at the Federal District Human Rights Commission stuck to their talking points, repeating their positions on the economy, crime, human rights and other issues.

Josefina Vazquez Mota, of the governing National Action Party, or PAN, said she favored opening state-owned oil giant Petroleos Mexicanos, or Pemex, to private investment to create a modern oil firm, but she made it clear that she opposed an outright privatization of the energy company.

Andres Manuel Lopez Obrador, the candidate of a leftist coalition led by the Party of the Democratic Revolution, or PRD, said he would not privatize Pemex if sworn in as Mexico's next president on Dec. 1.

"We are talking about ending the corruption at Pemex, but not about selling Pemex," Lopez Obrador said.

The former Mexico City mayor, who is known for his slow delivery, was cut off several times because he went over the allotted time.

New Alliance Party, or PANAL, candidate Gabriel Quadri said opening Pemex to competition did not mean stripping the nation of its ownership of petroleum resources.

"Let Pemex take them on, let it improve, let it compete with the best companies in Mexico," Quadri said.

Peña Nieto skipped the debate even though organizers promised on their Web site that it would "take place in a neutral environment and with democratic criteria, without favoring any of the participants with treachery or advantages."

The PRI candidate sent a letter to the student movement, thanking it for inviting him to participate and acknowledging the group's contributions to Mexico's democracy.

Peña Nieto, however, noted that "the Yo Soy 132 movement has officially taken a political position against my project and my person."

"In a democracy, it is absolutely valid to openly come out against any person or project," Peña Nieto said in his letter, adding that the movement's position "does not guarantee the space of neutrality needed to organize a debate on equitable conditions."

"For this reason, I have decided to decline your kind invitation," the PRI presidential candidate said.

The protest movement started on May 11, when Peña Nieto visited the Universidad Iberoamericana and was jeered by students, who accused him of being a candidate "manufactured" by the powerful Televisa network.

Those in Peña Nieto's inner circle and some media pundits downplayed the incident, accusing the students of being agitators.

The students counterattacked by making a video that was posted on YouTube.

The criticism led to the birth of the "Somos mas de 131" (We Are More Than 131) movement, which took its name from the number of students who appeared in the video and later evolved into the "Yo soy 132" (I Am 132) movement when students from other universities joined the protests.

The movement's main demand is for impartiality in media coverage of political campaigns, but it has also come out against the candidate of the PRI, which governed Mexico from 1929 to 2000.

The 45-year-old Peña Nieto, who served as governor of the state of Mexico, has been the frontrunner in the polls ahead of the presidential election.

The weekly Consulta Mitofsky poll, which was released on Tuesday, showed Peña Nieto with the support of 44.4 percent of likely voters, while Lopez Obrador has 28.7 percent support, Vazquez Mota is drawing the backing of 24.6 percent of likely voters and Quadri is trailing the pack with only 2.3 percent support.

Wednesday night's debate provided the last opportunity for the candidates to square off face to face.

The May 6 and June 10 debates were organized by the Federal Electoral Institute, or IFE.

Mexico will hold its presidential election on July 1, selecting a successor to President Felipe Calderon.

Nearly 80 million Mexicans will be eligible to vote for a new president, 628 legislators and thousands of other officials in the general elections. EFE