U.S. Rep. Mac Thornberry

U.S. Rep. Mac Thornberry, R-Texas, chairman of the Armed Services Committee.

A sixth Republican congressman from Texas announced Monday he would not seek re-election in 2020.

U.S. Rep. Mac Thornberry, chairman of the Armed Services Committee, said in a statement that "it was time for a change."

The 13-term Republican has held the state's 13th district near the Texas panhandle since 1995. He overwhelmingly won re-election in 2018 with more than 80 percent of the votes cast.

"With over a year to go, I will continue to represent the people of the 13th district to the best of my ability," he said. "Our nation faces many difficult challenges, and none of us can relax our efforts to meet and overcome them, whether at home or around the world."

Nationally, 19 Republican U.S. House members are not seeking re-election compared to six Democrats, making it more difficult for the GOP to regain the majority.

"A quarter of the Texas House Republican Delegation has now retired – a staggering amount for the largest Republican delegation in Texas," Texas Democratic Party Executive Director Manny Garcia said in a statement. "Texas is the biggest battleground state. Republicans know it and Texas Democrats damn sure know it."

Other retiring Republican congressman from the Texas delegation are Rep. Kenny Marchant of Coppell, Rep. Will Hurd of San Antonio, Rep. Mike Conaway of Midland, Rep. Pete Olson of Sugar Land and Rep. Bill Flores of Bryan.