The Republican Party once won elections on national security. Back in 2004, incumbent George W. Bush maligned his Democrat opponent John Kerry as a weak "flip-flopper" on the Iraq war, convincing voters that the Republican ticket would lead America decisively during the "war on terror."

But after more than a decade of war, Americans have become increasingly critical of Bush-era foreign policy decisions. According to the pollster Gallup, 53 percent of Americans now believe the Iraq war was a mistake. And although 66 percent of Republicans still stand by the invasion, nearly a third of the party now regrets the misadventure.

"There really is a kind of international commitment fatigue among the general public and that includes a lot of Republicans," Colin Dueck, the author of Hard Line: The Republican Party and US Foreign Policy since World War II, told DW. "It's just simply the case the people are in no mood in this country for further military interventions overseas."

One of the more stunning foreign policy confessions came recently from an old GOP warhorse, former speaker of the house Newt Gingrich. A foreign policy hawk who led Republicans to congressional dominance in the mid-90s, Gingrich also ran for the GOP presidential nomination in 2012.

"I am a neoconservative," Gingrich told the Washington Times, referring to the hawkish wing of the Republican Party. "But at some point, even if you are a neoconservative, you need to take a deep breath to ask if our strategies in the Middle East have succeeded."

"It may be that our capacity to export democracy is a lot more limited than we thought," he said.

Filibustering the drone war

The Republican Party's foreign policy reckoning has been in the making since the 2010 congressional mid-term election, which transformed the grassroots Tea Party movement into an important caucus within the GOP. Many elected officials now identified with the Tea Party, such as Kentucky Senator Rand Paul, are conservatives cut from a different cloth. They support ultra-conservative economic policies at home, but oppose military interventions abroad.

Senator Paul has become the face of the Republican anti-war wing.

The Republican Party's internal foreign policy fault lines were put on public display last March. The junior senator from Kentucky sought to force the White House to answer his questions about the drone program. Paul wanted to know whether or not the Obama administration thought it had the authority to launch drone strikes against American non-combatants on US soil.

When he didn't receive an answer, Paul spoke on the floor of the Senate for 13 hours, delaying John Brennan's nomination for CIA director. The White House eventually took notice of the senator's filibuster and responded, publicly stating that it did not have the authority to launch such drone strikes on US soil.

In an ironic political twist, Senator Lindsey Graham - a leading Republican hawk - praised President Obama for adopting tough Bush-era counterterrorism policies while implicitly accusing his party colleague Paul of being soft on national security by taking issue with the drone program.

"And to my party, I'm a bit disappointed that you no longer apparently think we're at war," Graham said after the filibuster ended.

Paul, for his part, claimed that he was promoting "a healthy debate within the Republican Party," arguing that for too long Republicans had been "monolithic" on the war on terror.

Defunding NSA surveillance

The internal Republican battle over national security intensified during the summer, when the intelligence leaks by former NSA contractor Edward Snowden ignited a firestorm of controversy over post-9/11 surveillance policies.

Representative Justin Amash of Michigan, a Republican associated with the Tea Party, proposed an amendment to a defense appropriations bill that would have stopped funding for the NSA mass surveillance programs like PRISM. Those programs have their origins in Bush administration counterterrorism policies.

Leading Republicans sought to isolate Amash in the House.

"We're here today for a very simple reason: To defend the Fourth Amendment, to defend the privacy of each and every American," Amash told House members as he introduced the measure.

But Intelligence Committee Chairman Mike Rogers and six other Republicans sent a letter to the party rank and file, encouraging them to vote against the Amash amendment.

"While many members have legitimate questions about the NSA metadata program, including whether there are sufficient protections for Americans' civil liberties, eliminating this program altogether without careful deliberation would not reflect our duty, under Article I of the Constitution, to provide for the common defense," the seven Republicans wrote in the joint letter.

Ultimately, the Amash amendment narrowly failed by a margin of just 12 votes. Republicans were deeply divided on the issue, with 93 voting for the measure and 134 against.

'A very dangerous thought'

Just days after Amash's amendment failed, New Jersey Governor Chris Christie took aim at Paul, calling "the strain of libertarianism" running through the Republican Party "a very dangerous thought." Both Christie and Paul are potential contenders for the 2016 Republican presidential nomination.

McCain (left) and Graham (right), leading hawks, regularly clash with Paul in the Senate.

But during the debate over possible military strikes against Syria last September, Republican lawmakers gravitated increasingly toward Paul's non-interventionist approach. According to a CBS tally at the time, 20 Republican senators were opposed to the strikes while 14 were undecided and only 8 were in favor. In the House, 155 Republicans were opposed to the strikes or were leaning toward opposing the strikes. Meanwhile, just 20 Republicans said they supported or were considering supporting military intervention.

According to foreign policy expert Dueck, Rand Paul is better positioned to make the non-interventionist argument today than his libertarian father, former Representative Ron Paul. The latter ran in the Republican presidential primaries in 2008 and 2012 on an anti-war platform. But Dueck says Rand has a long way to go if he wants to win over the party.

"The mood right now among a lot of Republicans is we don't want to have anything to do with Syria; we don't want to have anything to do with Libya - our main concerns are domestic; our main concerns are fiscal," Dueck said.

"[But] even after all of the frustration of Iraq and even after everything that's happened in the last decade, most Republicans tend to be more hawkish than the average American and significantly more hawkish than the average Democrat on defense and foreign policy issues," he said.