Congressman who broke with the Republican party in the vote against Mayorkas will not seek re-election

Rep. Mike Gallagher, Republican of Wisconsin, announced Saturday that he would not run for re-election, just days after breaking with his party to cast a tie-breaking vote against impeachment charges against Alejandro N. Mayorkas , the Secretary of Homeland Security.

Mr. Gallagher, who is in his fourth term in Congress, joins dozens of other lawmakers who have decided to quit. But the timing of his decision was nonetheless striking, coming on the heels of his impeachment vote — which had already given him one of the top challengers — and his relative youth, compared to others planning to withdraw from Congress.

“Electoral politics should never have been a career and, believe me, Congress is no place to grow old,” Gallagher, 39, said in a statement, adding that he made the decision not to run “with pain in the heart. .”

Mr. Gallagher, a Marine Corps veteran and former congressional staffer, was an influential voice in the House of Representatives on issues of national security and the military. He has been particularly outspoken about the wars in Afghanistan and Ukraine, as well as cybersecurity, having co-chaired an intergovernmental commission on the issue early in his congressional career.

When House Speaker Kevin McCarthy picked him last year to lead a new committee charged with investigating threats from the Chinese Communist Party, he was the youngest Republican to wield the gavel of a panel .

Mr. Gallagher also caught the attention of Senate Republican canvassers, who tried to convince him last year to run against Senator Tammy Baldwin, Democrat of Wisconsin. But Mr. Gallagher decided to abandon that bid and announced at the time that he would stand for re-election to the House of Representatives.

However, his position in the Republican Party appeared to have changed earlier this week after he became the third Republican in the House of Representatives to refuse to support the impeachment of Mayorkas. The charges of refusing to enforce the law and breaching the public trust were widely dismissed by legal experts as not meeting the constitutional threshold of high crimes and misdemeanors.

The effort to oust Mr. Mayorkas failed by just one vote.

“Impeachment proponents have failed to argue how his staggering incompetence meets the impeachment threshold,” Mr. Gallagher said in a statement this week defending his decision, arguing that Mr. Mayorkas’ impeachment “is a dangerous new would set a precedent that would be weaponized against future Republican administrations.”

The House of Representatives is expected to try again to impeach Mr. Mayorkas next week, once Representative Steve Scalise of Louisiana, the second House Republican to be absent while undergoing treatment for blood cancer, returns to Washington.

Mr. Gallagher did not say exactly what he planned to do next, although he indicated his next role would also be in national security.

“While my title may change, my mission will always be the same,” he said in a statement. “Deter America's enemies and defend the Constitution.”