For many years, Senator Lindsey Graham traveled the world together with his good friend John McCain, visiting conflict zones and assembly with overseas allies and adversaries, earlier than returning residence to advertise the Republican gospel of an internationalist, hawkish overseas coverage.

However this week, after President Biden introduced that troops would leave Afghanistan no later than Sept. 11, Mr. Graham took the rostrum within the Senate press gallery and hinted that spreading the celebration’s message had turn into a bit lonely.

“I miss John McCain lots however most likely not more than right this moment,” Mr. Graham mentioned. “If John had been with us, I’d be talking second.”

Mr. McCain, the onetime prisoner of conflict in Vietnam, in some ways embodied a particular Republican worldview: a dedication to internationalism — and confrontation when mandatory — that stemmed from the Chilly Warfare and endured by way of the presidencies of Ronald Reagan and George H.W. Bush earlier than evolving after the Sept. 11 assaults to account for the specter of international terrorism.

Then got here Donald J. Trump, who campaigned on a promise to place America first, an isolationist mantra that resonated with a nation weary of countless wars. Now, out of energy in Washington, Republicans have splintered into disparate factions, with few figures to take the lead.

Within the Senate, lawmakers who constructed reputations as leaders on overseas coverage — like Mr. McCain and Senators Richard Lugar and John Warner — are lengthy gone. Mr. Trump defenestrated a lot of the celebration’s policymaking institution by alienating dozens of overseas coverage specialists, who refused to help his marketing campaign, not to mention enter his administration.

And for formidable Republican officers, the political calculation stays stark: To the extent that Republican voters care in any respect about overseas coverage points, many have come to embrace Mr. Trump’s nationalistic views on points like commerce, abroad navy ventures and even Russia.

“Boy, I’m hard-pressed,” mentioned Chuck Hagel, the previous Republican senator, when requested to call a G.O.P. overseas coverage professional within the Senate. “The emphasis on overseas coverage most likely hasn’t been the identical with senators. However I can’t consider a Dick Lugar or a John Warner or any of the blokes I served with.”

Mr. Graham, who made an unsuccessful run for president and was all the time overshadowed by Mr. McCain as a Republican voice on overseas coverage, spoke for greater than half an hour at a information convention on Wednesday, strolling listeners by way of a historical past of the Afghan battle.

“That is what they’re able to doing after we ignore the specter of the enemy,” he mentioned, gesturing to a big picture of a burning World Commerce Tower. “The chance of this and this taking place once more goes by way of the roof after President Biden’s choice right this moment.”

Different main Republicans, a few of whom condemned Mr. Trump’s pledge to withdraw all troops from Afghanistan by Might 1, additionally pressed the standard Republican viewpoint of utilizing American may to guard the nation’s pursuits.

Mitch McConnell, the Senate minority chief, warned that pulling out the troops can be a “grave mistake.”

“Apparently, we’re to assist our adversaries ring within the anniversary of the 9/11 assaults by gift-wrapping the nation and handing it proper again to them,” he mentioned in a speech on the Senate flooring.

However that view was removed from uniform. Senator Rand Paul, lengthy a vocal opponent of overseas intervention, mentioned he was “grateful” to Mr. Biden. “Sufficient countless wars,” he tweeted. Senator Ted Cruz informed CNN that he was “glad the troops are coming residence.”

And Senator Josh Hawley of Missouri, who has ambitions of creating a brand new coverage framework for the celebration, praised the choice.

“President Biden ought to withdraw troops in Afghanistan by Might 1, because the Trump administration deliberate, however higher late than by no means,” he mentioned. “It’s time for this without end conflict to finish.”

The dispute is hardly new, or contained to the G.O.P. Many Democrats have come to imagine that overseas coverage ought to serve home financial and political objectives way more closely than up to now. However Senator Jack Reed, the Democratic chairman of the Senate Armed Companies Committee, has warned that a full withdrawal from Afghanistan might pose a big nationwide safety menace.

For Republicans, the shift inward comes as their lengthy dominance over problems with nationwide safety and worldwide affairs is waning. Mr. Trump rejected Republican overseas coverage orthodoxy however largely struggled to articulate a cohesive countervailing view past a imprecise notion of placing America first. He embraced strongmen, solid longtime allies as free riders and favored a transactional strategy, rejecting any notion of the sort of values-driven overseas coverage that had outlined the celebration for many years.

The celebration’s overseas coverage institution discovered itself exiled from Mr. Trump’s authorities and preventing for relevance towards an rebel isolationist celebration base.

“To say that there’s a single Republican overseas coverage place is to overlook what’s been taking place inside the conservative motion on these subject for the final 20 years,” mentioned Lanhee Chen, a Hoover Establishment scholar and coverage adviser to plenty of distinguished Republican officers. “The characters change, the terminology adjustments, however the variations stay.”

But, that previous debate carries new political resonance for the celebration, because it confronts the political must develop a platform that goes past merely opposing regardless of the Democratic administration places in place.

“Anytime you don’t have the White Home and also you don’t have management of the Congress, it’s a time to look inward and work out what the predominate view is,” Mr. Chen mentioned.

With the Republican base extra centered on points like relitigating the election and so-called cancel tradition, there was little dialogue about what bigger agenda the celebration ought to pursue. However some specialists see a chance for Republicans to articulate a brand new conservative perspective on nationwide safety points.

Overseas coverage, notably withdrawing from Afghanistan, was one of many few areas the place Republican elected officers had been prepared to publicly criticize Mr. Trump. Now that he has left workplace, overseas coverage specialists who condemned Mr. Trump all through his administration, and endorsed Mr. Biden by the handfuls, are hopeful that celebration consensus will revert to the standard Republican values of free commerce, extra open immigration and a re-embrace of worldwide alliances.

“Restoration does really feel like the suitable phrase, each within the long-shot nature of it occurring, and within the correction to what have lengthy been recognized as conservative insurance policies,” mentioned Kori Schake, who directs overseas and navy coverage research on the conservative American Enterprise Institute and served on the Nationwide Safety Council below President George W. Bush.

But probabilities that Republicans will obtain a whole restoration of the standard celebration platform appear low, notably if Mr. Trump continues to flex his political energy amongst his base. The previous president captured the hearts and minds of his followers, shifting opinions on problems with globalism. Throughout his administration, polling confirmed Republican voters adopted a extra optimistic view of Russia and have become extra skeptical of commerce agreements and worldwide alliances.

A survey performed by the Chicago Council on World Affairs final 12 months discovered that Republican voters most well-liked a extra nationalist strategy, valuing financial self-sufficiency, and taking a unilateral strategy to diplomacy and international engagement

When requested in regards to the results of the coronavirus pandemic, 58 p.c of Republicans surveyed mentioned the outbreak confirmed america must be much less reliant on different nations, in contrast with simply 18 p.c of Democrats who mentioned the identical. Near half of Republicans agreed that “america is wealthy and highly effective sufficient to go it alone, with out getting concerned within the issues of the remainder of the world,” and two-thirds mentioned they most well-liked that the nation produce its personal items, versus shopping for or promoting abroad.

One other survey by Tony Fabrizio, one in every of Mr. Trump’s pollsters, discovered that solely 7 p.c of Republicans prioritize nationwide safety and overseas coverage points, in contrast with practically 1 / 4 who care about financial points.

“We don’t wish to have interaction in nation constructing, we don’t wish to have interaction in countless police actions,” mentioned John McLaughlin, who additionally performed polling for Mr. Trump. “President Trump was forward of the curve when he was saying we have to have an American first coverage, and that’s the place public opinion is inside the celebration.”

A lot of that debate could play out within the early phases of the 2024 presidential race, as Republican contenders try to burnish their overseas coverage credentials. Already, some are casting themselves as heirs to the Trump legacy, with Mike Pompeo, the previous secretary of state, and Nikki Haley, the previous ambassador to the United Nations, broadly assumed to be weighing presidential bids.

Mr. Pompeo, who not too long ago grew to become the co-chairman of a brand new overseas coverage group on the Nixon Basis that goals to reassert “conservative realism,” mentioned he supported Mr. Biden’s choice.

“Lowering our footprint in Afghanistan is totally applicable,” Mr. Pompeo mentioned in an interview on Fox Information. “It’s the suitable factor.”

The remark marked uncommon reward from a person who is emerging as the most outspoken critic of Mr. Biden amongst former prime Trump officers.

After all, because the Fox Information hosts identified, had Mr. Trump received re-election, the troops would have been coming residence subsequent month — with the complete help of Mr. Pompeo, if not many different Republican leaders.