Campaign front-runner Enrique Pena Nieto, of the Institutional Revolutionary Party, has acknowledged cheating on his former wife.
A billboard for AshleyMadison.com shows a photo of Pena Nieto wearing a white dress shirt with a red lipstick stain on the collar and a message that reads: "Unfaithful to His Family. Faithful and Committed to His Country."
The site's representative in Mexico is Ricardo Castaneda. He says that if the candidate had used it services "no one would have found out about the affairs." He says the company may feature other politicians in future billboards.
Pena Nieto spokesman Mario Sanchez says the campaign will issue a statement later.