Experts say PAN administrations have been unsuccessful because Fox and Calderon have faced stiff opposition in Congress, where many of their proposed reforms were diluted or killed.
Others blame corruption for the party's woes.
"The problem with the PAN is that it got into power and it started desperately stealing, and they stuffed themselves as if they were dying of hunger," said Manuel Clouthier Carrillo, a former PAN congressman whose father, Manuel Clouthier del Rincon, was among the party's founders.
Many PAN members are enraged that the PAN mayor of Monterrey, Fernando Larrazabal, wasn't kicked out of the party after a video showed his brother receiving wads of cash inside a Monterrey casino, whose owner claimed he was being extorted. He is currently running for a seat in the lower house of Congress.
"Instead of the PAN cleaning up the system, the system corrupted the PAN," said Clouthier, who wants to run for the presidency as an independent. "It's incredible that after two terms of a PAN federal government, there hasn't been a single crusade against corruption."
Mexicans disappointed with the PAN now seem ready to return the PRI to the presidency despite its reputation as a corrupt party that retained power through fraud, political clientelism and by crushing dissent.
The conservative party is gambling that this country known for machismo is ready to be led by a woman and it picked Josefina Vazquez Mota, a 51-year-old economist and devout Roman Catholic as its presidential candidate.
Vazquez Mota, a mother of three, has presented a warm, affable image while pledging to improve public education and to make Mexico safer by continuing Calderon's plan to clean up police departments.
She has declared her one-word campaign slogan to be "Diferente," or "Different," in an apparent effort to distance herself from Calderon, whose approval rating has been dropping.
In launching her campaign last week, Vazquez Mota said she would look to build consensus among parties when governing unlike Calderon, whose cabinet is comprised of PAN allies.
But the former education minister and congresswoman faces an uphill battle against former Mexico State governor and PRI candidate Enrique Pena Nieto, who leads in recent polls.
Vazquez Mota's first pre-campaign and campaign events were marked by poor planning, small crowds, or disruptive hecklers. And on Monday, she suffered a dizzy spell during a speech to anti-crime activists and had to interrupt her speech, sit down and continue speaking while seated.
Later, Vazquez Mota told local media she may have suffered a drop in blood pressure, and said her health is good.
A poll by the Reforma daily newspaper published Wednesday showed Pena Nieto with a 13-point lead over Vazquez Mota.
About 45 percent of likely voters surveyed said they planned to vote for Pena Nieto. Vazquez Mota earned 32 percent of their support. Andres Manual Lopez Obrado of the leftist Democratic Revolution Party trails in third with 22 percent.
The poll, conducted by the newspaper surveyed 1,343 Mexicans between March 22 and 26. It had a sampling error margin of 2.7 percentage points.
Despite losing the presidency, the PRI has continued to govern most of Mexico's 32 states. It currently holds 19 governorships.
The PAN, long an elitist party of businessmen and other upper and middle-class, religious members, now also includes many working class and other people who grew disenchanted with the PRI. But Shirk said it never created the kind of mass-based system that kept the PRI in power for seven decades.
One of the PAN's big mistakes was not building a stronger party base for itself to replace the electoral machinery that the PRI had developed over many, many years," Shirk said. "The PAN had a very weak mass base and without that kind of a strong electoral connection to constituency the PAN was almost a virtual party."
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