Pinal County Sheriff Paul Babeu confirmed during a Saturday news conference he is gay and had a relationship with a man identified by The Phoenix New Times as Jose, but said he never threatened the man with deportation.
"I'm here to say that all these allegations that were in one of these newspapers are absolutely, completely false, except for the issues that refer to me as being gay. Because that's the truth: I am gay," Babeu said.
Jose told the New Times Babeu and his attorney tried to force him to sign a document agreeing never to publicly reveal their relationship.
"Jose came to our firm because he felt he was being intimidated, and he was in fear for his life," attorney Melissa Weiss-Riner told the New Times. "He wanted his legal rights protected."
Republican Babeu, 43, is known for be a staunch border-security hawk, The Arizona Republic said.
Arizona State University political scientist Bruce Merrill told the Republic the allegations could deal a fatal blow to the sheriff's campaign.
"You can't overcome that, if it's legitimate," Merrill said. "I would be surprised that he would even continue to stay in the race. That's the end of his political career."
Meanwhile, Babeu stepped down as the Arizona campaign co-chair for Republican presidential hopeful Mitt Romney Saturday.
"Sheriff Babeu has stepped down from his volunteer position with the campaign so he can focus on the allegations against him," Romney spokesman Ryan Williams said in a written statement. "We support his decision."