On Thursday, Congressman Charlie Dent, a Republican from Pennsylvania first elected in 2004, announced that he would not seek reëlection next year. Dent was the second House Republican this week to announce his retirement rather than run for office in what promises to be a challenging 2018 midterm election for the G.O.P.

Dent is the leader of a group of moderate Republicans in the House that calls itself the Tuesday Group, and he is well-known in Washington for speaking his mind against the rise of the far right in his party and the forces that elected Donald Trump. I caught up with him on Friday afternoon as he was driving back home from D.C. after voting for the deal that raised the debt limit and financed an aid package to help those affected by Hurricane Harvey. Dent was in a jovial mood as he reflected on the state of the modern G.O.P. and the age of Trump.

His restatement was a long time coming. He’d been thinking about it ever since the 2013 government shutdown, a seminal moment for the G.O.P., when the most conservative members of the House Republican conference steered the party into what moderates like Dent thought was an insane strategy of forcing a shutdown to leverage policy concessions from President Obama.

There was a recent rally in Dent’s district by about a hundred conservative activists who support his ouster, but Dent said the event, which was cheered by Breitbart, and the primary challenge from a local politician, Justin Simmons, didn’t affect his decision. “It was a buffoon bus, and it was a freak show,” Dent said. “That had nothing to do with it. This decision had been made.” As for Simmons, when the candidate attacked Dent for not being sufficiently supportive of Donald Trump, Dent released text messages between them in which Simmons, in 2016, inquired as to whether Trump could be booted off the Republican ticket. “He’s a phony,” Dent told me, noting that Simmons also texted him asking for his support in another campaign. “He’s out there trashing me while on the other hand he was begging for my endorsement.” He added, “It was fun to do that.”

During his time in Congress, Dent has had similar amounts of fun smacking around his colleagues to his right, which is one of the reasons that he has drawn opposition from the online conservative world. In 2016, he refused to vote for Trump and wrote in the name of Evan McMullin, the fiercely anti-Trump independent candidate. Earlier in the day, he had been at an event with John Kasich, the governor of Ohio, and John Hickenlooper, the governor of Colorado. Kasich is clearly mulling a primary challenge to Trump, and Dent did not rule out supporting a Trump opponent, noting that the President himself has been supporting challengers to Republican incumbents.

“It’s not helpful if the President is encouraging primaries against sitting Republican senators like Jeff Flake,” he said. “The more he does that, the more likely I think it is that he suffers the same fate. You keep hearing about the allies of the White House, like Breitbart, are encouraging this kind of thing, and it’s probably not helpful for the President going into 2020.”

Dent is in many ways a victim of the changes in his party that he traces back to 2013. “Washington has had a difficult time performing the basic tasks of governance in recent years, and I think this culminated, probably, in September or October of 2013, when the government shut down,” he said. “Back then it was, could we provide relief to Hurricane Sandy victims? Can we re-authorize the Violence Against Women Act? Can we prevent the country from going into default? Can we keep the government open? Can we ever reach a budget agreement? Basic fundamental tasks of government have become extraordinarily difficult to enact. And because of that, because so much energy is expended and wasted on those issues, it is very, very difficult for all of us to focus on major policy issues like tax reform, infrastructure, and health care. It’s very hard to take on big policy issues and make major changes if we can’t get the basics down.”

The former Speaker of the House, John Boehner, was a victim of those previous battles, and Dent said the current Speaker, Paul Ryan, is in danger of being toppled by the same forces. “The dynamics that led to the departure of John Boehner are still there to plague Speaker Ryan,” Dent said. “Paul knows that. He knew that when he took the job. Those dynamics are still there, and it’s hard to change those underlying dynamics.” It’s often assumed that Ryan is more popular with the right than Boehner was, but Dent wasn’t so sure. “Ryan’s position is probably a little bit more solid than Boehner’s,” Dent said. “The difference is the people who didn’t like John Boehner were direct with him. They told him they didn’t like him, and that they were going to try to take his legs out from under him. With Paul Ryan, a lot of them will say they like him and they want to help him, and then they’ll try to take his legs out from under him.”

Like many other Republicans who vote to raise the debt ceiling and avoid government shutdowns, Dent has been complaining about his colleagues to the right for years. Because Boehner and Ryan rarely had the votes to accomplish those basic tasks, they need Democrats, whose votes always come with a price tag and thus inevitably move the deals to the left. That is exactly what happened this week, when Trump caved to Nancy Pelosi and Chuck Schumer’s demands for a three-month extension of the debt ceiling that would allow the Democrats another moment of leverage in December. Ninety Republicans ended up voting against the deal, even though the Harvey aid was attached to it.

“Both under Speakers Boehner and Ryan, there’s been far too much consideration given to people who intend to vote no on a given matter, and not enough consideration is given for those who were voting yes on most matters,” Dent said of the Republican leadership’s kowtowing to the right. “They’ve spent a hell of a lot of time and energy trying to placate people who aren’t voting for the bills.”

Dent was particularly amused by the fact that Mick Mulvaney, the Office of Management and Budget director, came to the Hill on Friday to convince House Republicans to support the debt ceiling and Harvey deal. Mulvaney is a founding member of the Freedom Caucus, which precipitated the government shutdown in 2013 and whose members rarely support raising the debt ceiling. Dent missed the meeting, but his chief of staff gave him giddy reports about Mulvaney squirming in front of his old colleagues as he took the exact opposite position from that during his years in the House. “It was a beautiful thing,” Dent said. “We should’ve sold admission tickets for the performance.”

As for the future of his party, Dent predicted that 2018 could be a wakeup call. “Let’s be perfectly honest—this has been a pretty rough start for the Administration,” he said. “Starting with the ill-considered and poorly executed travel ban, to the way the Comey firing was handled, to Russia, to Charlottesville. It’s been rough, and it’s causing a lot of concern.”

A senior Trump adviser who champions exactly the ideas that Dent was talking about once told me that the real long-term effect of Trumpism will come over the next few electoral cycles. If Republicans like Dent, he suggested, retire, and are replaced by Trump-like candidates, the populist movement will have succeeded. We won’t know until next November if Dent is replaced by a self-proclaimed Trumpian populist, like Simmons, or an establishment Republican or a Democrat. But Dent’s retirement opens the way for the kind of replacement that the Trump adviser was hoping would occur. Dent is an early casualty of Trump’s takeover of the G.O.P. “It’s just been a tough several months, and it’s been pretty damn exhausting,” he told me.

Dent said that he placed the blame for the party’s difficulties on Trump and the right-wing populism the President has championed. “I am concerned about the three-headed monster of protectionism, isolationism, and nativism,” Dent said. “And sometimes there’s a touch of nihilism in this, too. These three attributes have infected both political parties to varying degrees. And these are not attributes of a great nation.”