– Republican U.S. Rep. Joe Barton, Texas' most-senior member of Congress, said Thursday that he won't seek re-election after a naked photo of him circulated online and a conservative activist released past messages of a sexual nature from him.

The photo of the 68-year-old Barton was posted on an anonymous Twitter account just before Thanksgiving and Barton apologized. But he also suggested he could be the victim of online exploitation by a woman he'd had a relationship with whose name has not been released.

About a week later, Tea Party organizer Kelly Canon revealed Facebook Messenger exchanges from 2012 in which Barton asked if she was wearing panties and made other sexual references. Now twice divorced, Barton was still married to his second wife at the time of their online exchanges.

Canon said her relationship with Barton never advanced beyond the messages. She said Barton hadn't apologized for them and that she hadn't asked him to — but she also called on him to resign so that his private life couldn't be used against him and other Republicans during 2018 elections.

In announcing that he would retire next year, Barton made no mention of the embarrassing revelations.

"I am very proud of my public record and the many accomplishments of my office," he said in a statement. "Now it is time to step aside and let there be a new voice."

Though his seat remains safely Republican, Barton this week had drawn a little-known challenger for Texas' March primary and could have faced others. After his retirement announcement, Texas Republicans began lining up to replace him.

Before Barton decided to retire, political pressure on him to quit had increased. The Republican Party chairman in his North Texas home county of Tarrant called on him to step aside this week, as did Republican members of the Texas state Senate.

A former oil and gas consultant, Barton was first elected in 1984. His retirement means seven of the state's 36 members of Congress won't seek re-election.