Freshman Rep. Scott DesJarlais told a reporter that he did have sex with the woman and talked to her about getting an abortion.
DesJarlais, whose election platform includes an opposition to abortion rights, told the Chattanooga Times Free Press on Friday, "There was no pregnancy and no abortion." He said he talked about an abortion to "get her to tell me the truth" about not being pregnant.
DesJarlais, a physician, said he pushed the issue because the woman wasn't showing signs of being pregnant "approximately four months from the time that I had been with her."
DesJarlais' endorsement of Romney still appears on the congressman's website, but a link to the presidential campaign site returns an "access denied" message.
The Romney campaign did not immediately comment.
The transcript of the conversation emerged this week. The congressman said he did not record the call made while he was in the process of getting divorced from his first wife.
"You told me you'd have an abortion, and now we're getting too far along without one," DesJarlais is quoted as saying in the transcript. "If we need to go to Atlanta, or whatever, to get this solved and get it over with so we can get on with our lives, then let's do it."
The revelations did not prevent DesJarlais from presiding over a quick pro forma session of the House in Washington on Friday. The congressman had cited that responsibility in declining to participate in a debate with his Democratic opponent, state Sen. Eric Stewart.
While the Tennessee Republican Party appears to be standing behind DesJarlais, other GOP leaders in the state like Gov. Bill Haslam and Sen. Lamar Alexander have sought to avoid being drawn in.
Haslam said he wanted to speak with DesJarlais before voicing an opinion, but didn't say when that conversation would take place. "I probably will speak to him at some point in time," he said.
Alexander said it wasn't his practice to "go around telling people what to do about issues like that.
"That's between the congressman and the voters in his district and his opponent," he said. "I know the voters of his district very well, and they're perfectly capable of making their own minds up."
DesJarlais in a radio interview blamed "a disgruntled, defeated ex-congressman, a vindictive ex-wife, and a desperate Democratic candidate" for dredging up details from his past.
Stewart in a press conference on Friday rejected DesJarlais comments.
"I'm the one to blame?" he said. "I didn't sleep with a patient, I didn't have an affair on my wife, I didn't—real or not real—record a conversation to coerce that patient and mistress to have an abortion."
The DesJarlais campaign has dismissed the details as "old news" that emerged in the last election cycle. But while the 2010 campaign did feature allegations raised during his divorce that he intimidated his ex-wife with a gun—and in one instance put a gun in his mouth for three hours—the abortion element was not public knowledge until this week.
DesJarlais said in the radio interview that he has remarried and has enjoyed a "near perfect" marriage for the last decade.
"I would hope that when the voters judge me, they judge me on the marriage I have now," he said.
Associated Press writer Jim Abrams in Washington contributed to this report.