Wisconsin Rep. Mike Gallagher said he will resign from Congress on April 19, following the four-term Republican’s announcement last month that he wouldn’t run for reelection.

“I’ve worked closely with House Republican leadership on this timeline and look forward to seeing Speaker Johnson appoint a new chair to carry out the important mission of the Select Committee on the Chinese Communist Party,” Gallagher said Friday in a statement.

“Four terms serving Northeast Wisconsin in Congress has been the honor of a lifetime and strengthened my conviction that America is the greatest country in the history of the world,” he added.

Gallagher’s announcement comes as the House GOP majority already was set to shrink, since it was Colorado Rep. Ken Buck’s last day in Congress.

After Gallagher’s resignation takes effect, Republicans will be down to 217 members in the 435-member House, likely until special elections are held in California and Ohio later this year to fill seats that were previously held by Republicans. There’s also an special election in New York next month which Democrats are projected to win.

Under Wisconsin state law, the vacancy in Wisconsin’s 8th District will not be filled until after the general election in November.

Gallagher’s announcement comes a week after the House passed a bill he led that would force ByteDance, the company that owns TikTok, to divest the company or lose access to its millions of U.S. users.

A self-proclaimed defense hawk and Marine Corps veteran, Gallagher focused largely on national security issues while in Congress.

He was one of three Republicans who earlier this year voted against impeaching Homeland Security Secretary Alejandro Mayorakas, a vote that came days before he initially announced his retirement plans.

Senate Republicans were recruiting Gallagher to challenge Democratic Sen. Tammy Baldwin this year, but he opted against a campaign before later deciding to leave Congress altogether.

He has repeatedly held the title of the fastest man in Congress, won by dominating the competition in the American Council of Life Insurers Capital Challenge, a three-mile race in which participants include members of Congress, the judiciary, political appointees, their staff and members of the media. CQ Roll Call has acted as a race sponsor.