Support for Mexican presidential hopeful Josefina Vazquez Mota, candidate of the ruling National Action Party (PAN), has fallen to its lowest level since the campaign began at the end of March, a poll showed on Tuesday.

The latest voter survey by pollster Consulta Mitofsky showed Vazquez Mota slipping 0.6 percentage points to 20.8 percent, nearly 18 points behind front-runner Enrique Pena Nieto of the opposition Institutional Revolutionary Party, or PRI.

Vazquez Mota's efforts to win the July 1 election have been undermined by public discontent with President Felipe Calderon's administration over rampant drug-related violence which has claimed some 55,000 lives since the start of 2007.

The PAN has also struggled to create enough jobs to cater for Mexico's growing population.

Support for Pena Nieto, 45, the telegenic former governor of the State of Mexico, inched down a tenth of a point to 38.4 percent, according to the latest Mitofsky poll, which was conducted between May 11 and 13.

Leftist Andres Manuel Lopez Obrador, the 2006 runner-up, gained half a point to reach 19.1 percent.

Some recent polls have showed Lopez Obrador overtaking Vazquez Mota, whose bid for the top job has also suffered from infighting within the PAN and mishaps on the campaign trail.

The Mitofsky poll showed that the PRI, together with allies the Greens, could win enough votes in congress for an absolute majority, which no ruling party has had for 15 years in Mexico.

The survey interviewed 1,000 eligible voters and had a margin of error of 3.1 percentage points, the pollster said.