* Leading opposition candidate trips up in public
* Poll shows gaffes have hurt his standing
* Pena Nieto carries hopes of Mexico's long dominant PRI
By David Alire Garcia
MEXICO CITY (Reuters) - For over two years Enrique Pena Nieto has lorded it over rivals as hot favorite to become Mexico's next president. But just weeks after he launched his campaign, that veneer of invincibility has started to crack.
The immaculately-groomed contender for the opposition Institutional Revolutionary Party, or PRI, has stumbled through a series of gaffes since registering his candidacy on November 27, denting his commanding lead in polls.
Ridicule for the former governor of the State of Mexico began pouring out of online social media early this month when he struggled to name a single book beyond the Bible that had influenced him -- at an event where he was presenting his own book.
Days later, Pena Nieto lurched into further embarrassment during an interview by getting wrong the minimum wage and the cost of corn tortillas, a staple Mexican food. He then capped it with an offhand remark about housewives that upset some women voters.
"It's not worth voting for someone who doesn't know what a kilo of tortillas cost or what the minimum wage is," said Maria Teresa Olvera, a 44-year-old office janitor who backed the PRI in the 2006 election. "It's put a lot of doubt in my mind."
An increasing number of other voters feel the same way about the telegenic Pena Nieto.
A survey in Puebla-based newspaper Cambio showed the past month has hurt him. Some 37 percent of respondents said his inability to correctly name books that had shaped his thinking had lowered their opinion of him.
Support for the 45-year-old in a head-to-head contest fell from November by three points to 34 percent, the poll showed.
With leftist hopeful Andres Manuel Lopez Obrador gaining traction, this helped cut Pena Nieto's lead over his closest rival to just eight points from 13 points in November.
Pena Nieto carries the hopes of the centrist PRI which views itself as the natural party of government, having ruled Mexico for 71 straight years until it was ousted in 2000.
Reviled by many Mexicans as authoritarian and corrupt, the PRI was wiped off much of the electoral map in the 2006 presidential election. But its fortunes have revived behind the youthful appeal of a new generation headed by Pena Nieto.
Now the PRI almost wields a majority in the lower house of Congress and a Pena Nieto victory in July could help break the legislative deadlock that has hamstrung President Felipe Calderon's conservative National Action Party, or PAN.
The PAN has run Mexico since defeating the PRI in 2000 but its support has been hit by weak economic growth and a brutal drugs war that has killed more than 45,000 people in the past five years.
But if Pena Nieto's support continues to fall in a bruising campaign, it would give Lopez Obrador and the PAN's candidate, who has not yet been picked, a real chance.
Pena Nieto's flubs have given fresh ammunition to his opponents, who like to depict the fresh-faced lawyer as a creation of the media, ignorant and devoid of substance.
Responding to the criticism, Pena Nieto said over the weekend that his adversaries were attacking him "out of fear."
"I may not remember the name of a book's author, but let it be clear, what I will not forget is the violence, the poverty and the desperation that Mexico is living through," he said.
Pena Nieto, who is married to a former soap opera star, has repeatedly pledged to tackle the poverty affecting around 52 million people in Mexico, or nearly half the population.
But he was still unable to give the minimum wage or the price of tortillas in an interview with Spanish daily El Pais last week. After badly undershooting both figures, he defended his statements by saying, "I'm not the woman of the house."
That led to a swift rebuke from his only female competitor, Josefina Vazquez Mota, the leading PAN presidential hopeful.
"I've been a cabinet minister twice. I've made important decisions, but I'm also extremely proud to be a mother and a housewife," she said. "Being a housewife should never ... be thought of as something pejorative or second class."
While governor of the State of Mexico, Pena Nieto gave few interviews, but his tilt for the presidency has pushed him out into the open, forcing him to think on his feet rather than relying on the scripted addresses that helped make his name.
Outside the governor's office, he has found a minefield.
One YouTube video showing Pena Nieto stammering, pulling faces and casting about for help in his struggle to come up with a book title has racked up 1.6 million hits. Other videos have since been uploaded to mock his command of English.
Pena Nieto has moved to douse the flames of controversy fast - only to have members of his family start other fires.
Soon after Pena Nieto suffered his "reader's block" at a book fair in Guadalajara, his teenage daughter trapped him in a fresh sideshow when she re-sent comments on micro blogging site Twitter that described his critics as "proletarians".
So far, analysts believe the damage to his campaign is not critical. But his ratings are heading in the wrong direction.
"We're going to see a drop, not an abrupt fall or total disaster," said Leo Zuckermann, a political analyst at Mexico's CIDE social sciences think tank.
(Additional reporting by Rachel Uranga; Editing by Dave Graham and Kieran Murray)