As tensions escalate with the Islamic State, Sen. John McCain, Gov. Rick Perry and Rep. Paul Ryan are among the Republican lawmakers calling for more military action against the militant group. (Julie Percha/The Washington Post)

A roiling national debate over how to deal with the radical Islamic State and other global hot spots has prompted a sudden shift in Republican politics, putting a halt to the anti-interventionist mood that had been gaining credence in the party.

The change is evident on the campaign trail ahead of the November midterm elections and in recent appearances by the GOP’s prospective 2016 presidential candidates, with a near-universal embrace of stronger military actions against the group that has beheaded two American journalists.

A hawkish tone has become integral to several key Republican Senate campaigns, with a group of candidates running in battleground states calling attention to their ties to veterans and their support for the U.S. military at every turn.

In contests in Iowa, Arkansas and Alaska — where Republicans are running for seats held by Democrats — the GOP candidates are military veterans and focusing much of their time extolling their expertise.

A thirst among many conservative activists for a more muscular U.S. foreign policy was clear over the weekend at a meeting of Americans for Prosperity, the tea-party-affiliated group backed by the billionaire Koch brothers. The loudest applause came when Sen. Ted Cruz (R-Tex.), a potential presidential candidate, called for bombing the Islamic State “back to the Stone Age.”

Texas Gov. Rick Perry speaks at the Defending the American Dream Summit sponsored by Americans For Prosperity in Dallas Aug. 29. (Mike Stone/Getty Images)

Even Sen. Rand Paul (R-Ky.), a leader of the GOP’s anti-interventionist wing who is seen as a top-tier contender for the 2016 presidential nomination, has joined in the calls for a more hawkish approach.

The GOP’s changing tenor on foreign policy underscores the extent to which the party continues to struggle to forge its identity in the wake of the George W. Bush presidency.

Libertarian-leaning conservatives gained momentum in part by criticizing the Iraq war and the growth of government on Bush’s watch in the form of the National Security Agency’s aggressive use of domestic surveillance.

Their heightened clout led to clashes with prominent GOP hawks such as Sen. John McCain (Ariz.) and New Jersey Gov. Chris Christie, who openly challenged Paul’s worldview as weak and dangerous.

The tensions came to a head last year, when a measure to curtail the NSA’s data collection was only narrowly defeated in the GOP-led House and served as a warning to Republican officials that the Paul wing was ascendant inside Congress and willing to challenge the party’s long-held positions on matters of foreign policy and national security.

But now, with a series of competitive Senate races poised to determine control of the chamber and the GOP facing a wide-open contest for its presidential nomination, growing public unease with the U.S. role in the world is prompting many Republicans to revert to a more familiar, anti-
isolationist stance.

Not only are Republicans calling broadly for military actions against the Islamic State, they are also accusing President Obama of failing to stand up to Russian President Vladi­mir Putin and not doing enough to stand by Israel amid its recent fighting with Hamas.

New polling illustrates the shifting currents in the GOP — with concern about U.S. engagement in the world rising sharply over the past year and party members increasingly alarmed at the Obama administration’s policies.

According to a Pew Research Center poll released last week, 46 percent of Republicans said the United States does “too little” to help solve global problems — a 28-point increase from the previous poll, last November. The percentage of Republicans who believe the U.S. does “too much” abroad has dropped from 52 percent to 37 percent.

“Things are moving back in that [hawkish] direction, reflecting the mood of most Americans who are angry at what they’re seeing,” said Brian Walsh, a former spokesman for the National Republican Senatorial Committee. “Candidates are responding to that, and it is a product of the atmospherics.”

William Kristol, editor of the Weekly Standard and a leading pro-interventionist voice on the right, said Republicans are moving back to their “inner hawkishness.” He said that some in the party had been “a little intimidated for a while . . . by the so-called libertarian moment” but that GOP candidates are now showing a greater willingness to extend their foreign policy statements beyond mere attacks on Obama.

“What heartens me is that [candidates] are going beyond that criticism and talking about the need for a different approach, about how we can’t freak out when someone mentions potentially putting boots on the ground,” Kristol said.

Recent moves by Paul illustrate how some top Republicans are still searching for the party’s foreign policy sweet spot.

Two months ago, the Kentucky senator, who had been a vocal critic of the war in Iraq, wrote a Wall Street Journal op-ed chiding advocates for expanding the U.S. troop presence on the ground there and deploying airstrikes. He wrote that “many of those clamoring for military action now are the same people who made every false assumption imaginable about the cost, challenge and purpose of the Iraq war.”

But with the Islamic State taking center stage in recent days, Paul has started to sound more sympathetic to an interventionist policy.

“If I were president, I would call a joint session of Congress. I would lay out the reasoning of why ISIS is a threat to our national security and seek congressional authorization to destroy ISIS militarily,” Paul said in a statement released by his office.

Doug Stafford, a Paul adviser, said Wednesday that the senator was never an isolationist or non-interventionist. Stafford pointed to an article published this week in the Federalist, a conservative news Web site, titled “Why Calling Rand Paul an Isolationist Is and Was Stupid,” as a summary of Paul camp’s view on the kerfuffle over his worldview.

The article says that “preferring a smaller international military footprint is hardly isolationism.”

Several party strategists said that this year’s midterms have offered an opportunity for the GOP to at least present the appearance of a unified front on foreign affairs.

In Iowa, GOP Senate candidate Joni Ernst, a lieutenant colonel in the Iowa National Guard, has reminded voters that she would be the first female combat veteran to serve in the U.S. Senate. She recently took two weeks off from campaigning to complete her annual training.

She has also discussed her own experience with sexual violence in the military and told ABC News last month that she would have supported “leaving additional troops in Iraq longer.”

In Arkansas, Republican Senate candidate Tom Cotton, an Army veteran, recently aired an ad showing him in fatigues with a somber narration on how “serious times demand serious leaders.”

Former Massachusetts senator Scott Brown, a retired Army National Guard colonel running for Senate in New Hampshire, has also turned intently to foreign policy in recent weeks, hosting a forum on “America’s leadership standing in the world” alongside McCain and sharply criticizing Obama.

A reckoning looms immediately after the midterms, when the presidential primary scramble begins.

Texas Gov. Rick Perry, for instance, has attached himself squarely with the pro-interventionist wing, criticizing those in his party who favor less military involvement at a time of rising Islamic extremism.

Perry warned the activists gathered for the Americans for Prosperity meeting that “America has to act to confront this evil, because if we don’t, the price is only going to go up from here.”

Grass-roots favorite Ben Carson, a doctor-turned-political activist, drew cheers when he declared, “when we get through with ISIS, it should be IS-was.”

The opening for a hawk in the GOP field has even enticed former U.N. ambassador John Bolton, who advocated for a muscular foreign policy during the George W. Bush administration, to consider a White House bid. Bolton’s political action committees have raised millions, and he visited Florida in August to stump for state Republicans.

The reemergence of the hawks is no doubt a response to the feelings of conservative activists such as Nancy Sterman, a grandmother and business owner who attended the Koch group’s meeting.

“ISIS, a global economy, military security, Obamacare — there’s a new crisis every week that adds to the frustration of the American people,” she said. “But, thankfully, people are waking up.”