AUSTIN, Texas (AP) — Republican U.S. Rep. Joe Barton, Texas' most-senior member of Congress, announced 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 Fa...