MEXICO CITY (Reuters) - Mexican presidential front-runner Enrique Pena Nieto has widened his lead over leftist rival Andres Manuel Lopez Obrador with less than two weeks to go until a July 1 election, according to a poll by the Reforma newspaper published on Tuesday.
The previous poll from the newspaper on May 31 showed only a 4 percent gap between the two candidates, raising questions about a closer-than-expected race.
But the latest survey showed support for Pena Nieto, the candidate of the opposition Institutional Revolutionary Party (PRI), climbing by four percentage points to 42 percent while Lopez Obrador fell by four points to 30 percent.
The result puts the Reforma daily in-line with nearly every other major poll where Pena Nieto is leading his rivals by double digits.
Josefina Vazquez Mota, candidate of the ruling National Action Party (PAN), is lagging in third place with 24 percent backing.
However, Vazquez Mota made a strong showing in the second televised debate on June 10 between the candidates, attacking both Pena Nieto and Lopez Obrador, and support for her rose one percentage point from the poll in May.
Lopez Obrador, the leftist former mayor of Mexico City, lost the 2006 election to President Felipe Calderon in a tight finish and contested the results, staging months of protests and rattling investors in Latin America's second-largest economy.
Some markets observers feared a repeat of the last election after seeing the Reforma poll last month but Lopez Obrador has said he will respect the vote results.
Lopez Obrador rejected Tuesday's Reforma poll as an error, though, and insisted he was leading the race.
"I think what happened here was a mistake, we are still ahead," Lopez Obrador said on the campaign trail.
Support for Lopez Obrador surged last month after the emergence of a student movement attacking Pena Nieto and the PRI, which ruled Mexico for 71 years before losing an election to the conservative PAN in 2000.
The PRI's long rule was spotted with accusations of corruption and repression and the students say a vote for Pena Nieto would be a return to the past, rejecting the photogenic 45-year-old's claim that he represents a new face of the PRI.
Tuesday's poll showed 41 percent of those surveyed had a positive opinion of the student movement after large anti-Pena Nieto marches in Mexico City.
Many of the students have rallied around the candidacy of Lopez Obrador, seen as an alternative to the conservative government and the PRI.
Most of that support, though, is concentrated in traditionally more liberal Mexico City and the center of the country where Lopez Obrador is leading Pena Nieto by 3 percentage points, the poll showed.
In the rest of the country Pena Nieto still holds his strong lead and thirty percent of respondents said they had not heard of the student protests.
Even if Lopez Obrador does not win the race, the recent boost for his candidacy raises the possibility that the leftist Party of the Democratic Revolution (PRD) will have a strong showing in Congress, denting the PRI's majority.
Pena Nieto is promising to move forward on much needed fiscal and energy reforms that stalled under Calderon but he will face an uphill battle with a divided Congress.
The Reforma poll showed the PRI, in coalition with the smaller Green Party, winning the most seats in the lower house of Congress and Senate.
The PRD, along with an alliance of leftist parties that have opposed reforms in the past, will be second-strongest power in the legislature, the poll showed.
The Reforma poll surveyed 1,515 voters between June 14 and 17 with a margin of error of 2.8 percent.
Additional reporting by Dave Graham; Editing by David Brunnstrom