FILE – In this June 14, 2017 file photo, Rep. Joe Barton, R-Texas, speaks during a news conference on Capitol Hill in Washington. Barton, Texas’ most-senior member of Congress, announced Thursday that he won’t seek re-election following a nude photo of him that circulated online, as well as revelations that he exchanged separate messages of a sexual nature with a Republican activist. (AP Photo/J. Scott Applewhite) WASHINGTON (AP) Republican U.S. Rep. Joe Barton, Texas’ most-senior member of Congress, announced Thursday that he won’t seek re-election after a nude photo of him circulated online and a Republican activist revealed messages of a sexual nature from him. Barton, 68, initially apologized for the explicit photo that surfaced on Twitter just before Thanksgiving but refused to heed calls that he not seek re-election in 2018. Barton suggested he could be the victim of online exploitation. About a week later, tea party organizer Kelly Canon came forward with Facebook Messenger exchanges from 2012 when Barton asked if she was wearing panties and made other sexual references. Canon said Barton hadn’t apologized and that she hadn’t asked him to, but also called on him to resign to avoid an electoral “feeding frenzy” among Democrats. MORE: Sen. Franken back to work amid sexual misconduct allegations That prompted Barton to reverse course and announce that he was forgoing what would have been his 18th congressional campaign. Though his seat remains safely Republican, Barton had drawn a little-known challenger for Texas’ March primary and could have drawn more. He was first elected to Congress in 1984. His retirement means seven of the state’s 36 members of Congress aren’t seeking re-election. Pressure had intensified for Barton to quit. Republican Party chairman in Barton’s home county of Tarrant joined many conservatives in calling for Barton to step down after the nude photo. And following Canon’s revelation, Republican members of the Texas’ state Senate joined the call. Barton, who is from Ennis, Texas, was the manager of the Republican team that was practicing for a charity congressional baseball game in June when a gunmen opened fire, gravely injuring House Majority Whip Steve Scalise. MORE: The (incomplete) list of powerful men accused of sexual harassment after Harvey Weinstein