Rep. Charlie Dent (R-Pa.) likes to say he’s from the “governing wing” of the Republican Party, which is a helpful summary of how the Pennsylvania Republican approaches his responsibilities. In an era of radical Republican politics, with GOP “moderates” in short supply, Dent has seen his party jump off a right-wing cliff – and he’s refused to follow.

As the Morning Call reported last night, after nearly three decades of serving in elected office, Dent has apparently seen enough.

Republican U.S. Rep. Charlie Dent stunned his colleagues and constituents Thursday evening when the seven-term Lehigh Valley lawmaker announced that he will not seek re-election next year. […] Dent, 57, said his decision against an eighth term was one that had been building since 2013 and became final in mid-summer, after consulting with his family, close friends and senior staffers.

The GOP lawmaker said his thinking was “driven by personal matters,” though he added that conditions in D.C. were “a factor, to be sure.” Dent told the Morning Call that “even the most simple basic tasks of government have become excruciatingly difficult.”

His departure probably won’t help matters. As The Atlantic’s James Fallows noted, Dent was one of the few congressional Republicans who “looked for solutions, not tribal war.” It’s not that the Pennsylvania congressman relied on a center-left ideology – the era of “Rockefeller Republicans” has long since passed – but Dent has long believed in compromise and constructive policymaking.

And that left him out of step with the contemporary GOP, to the point that Dent did not vote for his party’s 2016 presidential ticket. As he put it last year, Donald Trump was simply “a bridge too far.”

Looking ahead, as the ideological median of the party moves even further to the right, it’s worth considering what retirement announcements like these tell us about Republicans’ national direction.

There are really only a handful of GOP lawmakers who deserve the “moderate” label – Dent, Florida’s Ileana Ros-Lehtinen, Washington’s Dave Reichert – but they have something important in common: they’ve all been marginalized in their radicalized party and they’re all calling it quits, stepping down at the end of this Congress.

By January 2019, the number of GOP voices on Capitol Hill, making a genuine effort to drag their party towards the mainstream, will be vanishingly small.