Lenin Carballido narrowly won Sunday's election in San Agustin Amatengo, near the colonial city of Oaxaca.
But then a death certificate surfaced, indicating that Carballido had died in 2010 of a diabetic coma.
Officials in Oaxaca today said the certificate had been drawn up and signed by a public registry official, but the death had been faked.
Prosecutors say one of Carballido's relatives used the death certificate to convince detectives to drop an arrest warrant for an alleged 2004 rape.