Kevin McCarthy formally ended one of the most lamentable political careers in American history Sunday, when he resigned from the US House seat he had occupied since 2007.

Tellingly, hardly anyone noticed. Everyone seemed to be ready to forget that the last of “The Young Guns”—the moniker once adopted by McCarthy along with fellow failed Republican leaders Paul Ryan and Eric Cantor—had ridden out of town. McCarthy says he plans “to serve America in new ways.” In reality, McCarthy is serving McCarthy, shamelessly setting himself up for what most observers expect will be a new career as an influence peddler, er, lobbyist.

But McCarthy’s departure was notable for one amusing, and politically significant reason. With the end of his tenure as the representative from California’s 20th Congressional District, McCarthy—in what appears to be a fit of pique—screwed over the House Republican Caucus that he had led until his unceremonious removal from the speakership last fall. By choosing to quit at the end of 2023, McCarthy took with him the one thing he had to offer his fellow partisans: protection for their rapidly dwindling majority.

With the expulsion of New York Representative George Santos on December 1 of last year, the Republicans were left with a four-seat cushion in the House—one of the narrowest majorities in the chamber’s history. And Republicans knew that majority was going to get even narrower, as Ohio Representative Bill Johnson had indicated months ago that he would be resigning early in 2024 to take up a lucrative position as president of Youngstown State University.

With McCarthy’s kiss-off to the caucus, and with Johnson’s planned exit on January 21, Republicans will be left with a nail-bitingly narrow 219-213 majority—meaning that, if just two Republican representatives fail to show up for a party-line vote, or if they reject the party whip for whatever reason, the Democrats could get the upper hand.

Practically, what this means is that House Speaker Mike Johnson (R-La.) and his fractious caucus, find themselves in a historically precarious position as Congress prepares to take up a wide range of contentious domestic and foreign policy issues—including the question of whether the federal government will literally shut down. It’s true that special elections that will be held in coming months could build out the GOP majority a bit. But that’s not guaranteed; indeed, Santos’s seat could very well flip to the Democrats.

There’s simply no question that the GOP’s circumstance in the House has been made worse by McCarthy’s decision to put his personal bitterness ahead of party loyalty.