By Reuters Mexican presidential front-runner Enrique Pena Nieto has become the unwitting poster boy for a website promoting adultery after he admitted cheating on his first wife. A new Mexican billboard by ashleymadison.com, a site that helps married people arrange affairs, shows Pena Nieto with an index finger over his lips in a hushing gesture. Next to him are the words: "Unfaithful to his family. Faithful and committed to his country." Pena Nieto, candidate of the opposition Institutional Revolutionary Party (PRI), has said he fathered two children out of wedlock by different women while married to his first wife. The billboard, mounted above a busy avenue in Mexico City, shows the 45-year-old with bright red lipstick on his collar. His campaign had no immediate comment on the advertisement. Ricardo Castaneda, Ashley Madison's representative in Mexico, said the billboard was put in the capital this week and that others are planned for the cities of Monterrey and Guadalajara. Castaneda told Mexican media no one would have found out about Pena Nieto's extramarital affair, if the presidential hopeful had employed Ashely Madison's services. The masthead on the company's website reads "Life is short. Have an affair," and Castaneda said the service has acquired 300,000 users since opening for business in Mexico in November, making it Ashley Madison's fastest growing market. Pena Nieto's looks have made him popular among women, who make up a majority of eligible voters in Mexico. He is often mobbed by screaming female followers on campaign. Pena Nieto's first wife, who died in 2007, bore him three children. He is now married to a popular soap opera star and is favorite to win the July 1 presidential election.