Mexico's presidential frontrunner faces mounting protests

Less than three weeks before Mexicans go to the polls to choose a new president, frontrunner Enrique Peña Nieto is coming under increasing pressure from some sectors who fear the return to power of the Institutional Revolutionary Party (PRI).

Peña Nieto, a former state governor, squared off with his three top rivals in a televised debate on Sunday broadcast from Guadalajara, while an estimated 90,000 people held an anti-PRI protest in Mexico City.

The race has tightened over the last few weeks with leftist candidate Andrés Manuel López Obrador, who lost by a narrow margin in 2006 to conservative Felipe Calderón of the National Action Party (PAN), closing the gap on the PRI contender.

A recent poll conducted by the Mexico City daily El Universal along with Buendía&Laredo gave Peña Nieto 43.8 percent and López Obrador 27.7 percent. Josefina Vázquez Mota of the ruling PAN, was close behind on 26 percent while a fourth candidate, Gabriel Quadri de la Torre of the New Alliance party, polled less than three percent. Although the PRI is in the lead, the poll also showed that support for Peña Nieto has dropped by 10.5 points since April while López Obrador's popularity has swelled by six points in the same period.

Protestors fear a return to times when PRI governments were plagued with cronyism and corruption

President Calderón, who is barred from running for another term, said on Wednesday that any of the three top contenders could win on July 1. "In my opinion, any of the candidates at this time, especially the three top contenders, can win the race," Calderón told reporters.

Fearing a return to a past when PRI government were plagued with cronyism and corruption, protestors have been using the online social media to remind voters of the historic party's checkered past when it governed Mexico from 1929 to 2000.

Peña Nieto has tried to convince voters that the PRI has changed during the 12 years it has been out of power.

But the frontrunner has now had to refute new allegations contained in documents obtained by Britain's The Guardian newspaper that the nation's biggest broadcaster Televisa slanted its news coverage in favor of Peña Nieto while he was the governor of Mexico State, grooming him for the PRI candidacy.