WASHINGTON (AP) — Republican Rep. Ed Royce of California said Monday he will not seek re-election after serving out his 13th term in the House, the latest in a string of committee chairmen who have announced their retirement.

Royce is the chairman of the House Foreign Affairs Committee. This was to be his final year as chairman regardless of whether he sought re-election. He said he would spend his final year fully focused on the "urgent threats facing our nation."

But it's also clear the congressman was facing one of the most challenging elections of his career. In last year's presidential election, Democrat Hillary Clinton defeated Republican Donald Trump in California's 39th Congressional District. That prompted the campaign arm for congressional Democrats to target Royce's district in Southern California as one they hoped to flip in their midterm effort to take control of the House. Royce won in 2016 with more than 57 percent of the vote.

Royce became the 29th House Republican to announce a decision not to seek re-election this year, compared to 14 Democrats. With Trump's popularity in the dumps and a string of election victories in recent weeks, Democrats have hopes of gaining the 24 seats they would need to win control of the chamber.

In a press release announcing his retirement, Royce cited the tax cut bill passed in December and the crackdown on the global ivory trade as among recent accomplishments.

Republican Rep. Steve Stivers, the chairman of the National Republican Congressional Committee, said the GOP was "fired up and ready to hold this seat."

"We have just one message for Democrats who think they can compete for this seat: Bring it on," Stivers said.

Democrats said that Royce's retirement was another sign of the party's growing momentum going into the midterm elections.

"In a district that Hillary Clinton won by 8 points, Democrats are poised to win this Orange County seat and send someone to Washington who truly represents the values of Southern California," said Drew Godinich, a spokesman for the Democratic Congressional Campaign Committee.