Enrique Peña Nieto, the presidential candidate of Mexico's main opposition Institutional Revolutionary Party, or PRI, has expanded his lead over ruling party standard-bearer Josefina Vázquez Mota, a new poll indicates.

The PRI hopeful is ahead of the conservative National Action Party nominee by 34 percent to 21 percent, according to results from polling firm GEA-ISA published Tuesday by capital daily Milenio.

Peña Nieto led Vazquez Mota by 7 percent in a survey carried out last month.

Mexico Ruling Party Picks First Woman Presidential Candidate

GEA-ISA's latest poll shows leftist candidate Andres Manuel López Obrador with backing from 15 percent of likely voters, while the proportion of people describing themselves as undecided increased from 17 percent in February to 29 percent this month.

The company conducted in-home interviews with 1,146 potential voters during the period March 17-19. The poll has a margin of error of plus/minus 3 percent.

Mexico is Out to Set the Record on Breaking World Records

The PRI ruled Mexico without interruption from 1929 until 2000, when National Action's Vicente Fox won the presidency with support from across the political spectrum, but the conservatives barely held on to power in 2006, as Felipe Calderón defeated López Obrador by a mere 0.56 percent of the vote amid accusations of fraud.

Mexico's constitution limits the president to a single six-year term.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino