A small handful of House Republicans sided with Democrats earlier this week and voted against impeachment for Homeland Security Sec. Alejandro Mayorkas over his apparent refusal to fully enforce existing border security and immigration laws.

Following immediate backlash over that vote, Rep. Mike Gallagher (R-WI) announced that he would retire from Congress at the end of the current term and not seek re-election, the Daily Wire reported.

Gallagher's retirement decision comes amid reports that an outspoken supporter of former President Donald Trump, GOP consultant, and strategist Alex Bruesewitz, signaled his intention to mount a primary challenge against the Wisconsin incumbent who was previously considered to be a young rising star for the Republican Party.

Not seeking re-election for another term

Rep. Gallagher, who formerly served as a U.S. Marine Corps intelligence officer before he was first elected to Congress in 2016, said in a statement on Saturday, "Eight years ago, I promised to treat my time in office as a high-intensity deployment."

"Through my bipartisan work on the Armed Services and Intelligence Committees, chairing the Cyberspace Solarium Commission, and chairing the Select Committee on the Chinese Communist Party, we’ve accomplished more on this deployment than I could have ever imagined," the veteran congressman continued.

"But the Framers intended citizens to serve in Congress for a season and then return to their private lives," Gallagher said. "Electoral politics was never supposed to be a career and, trust me, Congress is no place to grow old. And so, with a heavy heart, I have decided not to run for re-election."

The Wisconsin Republican from Green Bay thanked his constituents for the "honor of a lifetime" and said his four terms in Congress had further convinced him that "America is the greatest country in the history of the world," and added, "And though my title may change, my mission will always remain the same: deter America's enemies and defend the Constitution."

Was likely to face a strong primary challenge

The Hill reported that Rep. Gallagher, one of three House Republicans to vote against impeachment for DHS Sec. Mayorkas, explained in an op-ed that while he viewed the secretary as a "disgrace," he could not bring himself to support the effort to remove him from office due to his concerns about the precedent such an action would set going forward.

"I disagree with my Republican colleagues who voted on Tuesday to impeach Mr. Mayorkas," he wrote. "Impeachment not only would fail to resolve Mr. Biden’s border crisis but would also set a dangerous new precedent that would be used against future Republican administrations."

That explanation will likely prove insufficient to satisfy critics outraged over Gallagher's "No" vote on impeachment, such as Trump ally Bruesewitz, a Wisconsin native who currently resides in Palm Beach, Florida, and had previously eyed Gallagher's seat when it was rumored the congressman would run for the Senate this year but backed down when that idea didn't pan out.

Following the impeachment vote, Bruesewitz said in an X post, "Mike Gallagher is a disgrace to my home state of Wisconsin and the Republican Party. @RepGallagher just voted against the impeachment of Sec Mayorkas, the man who has worked hand and hand with Biden to open our borders and allow dangerous criminals to flood into our country."

"Gallagher made a swampy back room deal, also known as Quid pro quo, to save Mayorkas’ a** and sellout his fellow Republicans. Unforgivable!" he added.

Dozens of members leaving Congress after this term

Roll Call reported that Rep. Gallagher is the 13th House Republican -- and the 24th House member overall -- to announce that they will retire from Congress at the end of the current term. His 8th District seat is in little danger of being flipped, though, as it is widely considered to be a solidly GOP seat.

Axios also reported that Gallagher, who chaired the select committee on China, is the fourth Republican committee chair to head for the exit -- along with several other senior GOP members -- in what has shaped up to be a historic and record-setting cycle in terms of the rate of retirements by incumbent members.