Story highlights

Candidates grappled with how best to defeat ISIS, the balance between security and privacy and the wisdom of regime change

Contentious exchanges exposed fault lines at the center of the GOP, deepened by more than a decade of conflict abroad

Washington CNN  — 

Only one Republican presidential candidate – long-shot South Carolina Sen. Lindsey Graham – admits to missing George W. Bush.

But seven years after the 43rd president left office, his controversial foreign policy is back in the spotlight, as Republican presidential candidates grope for a new conservative foreign policy consensus on the tough national security issues such as terrorism and the Middle East that shaped his presidency and will test the next inhabitant of the Oval Office.

After a 2016 campaign so far memorable for theatrics and vitriol, substance finally broke through at the last Republican debate of the year, held Tuesday night amid the artificial splendor of the Venetian casino in Las Vegas.

Candidates grappled with how best to defeat ISIS, the balance between security and privacy and the wisdom of regime change in the fractious Muslim world. They sparred over American boots on the ground in Syria as well as how to handle Russian President Vladimir Putin.

READ: 5 takeaways from the CNN Republican debate

On one side of the line, New Jersey Gov. Chris Christie reintroduced some of the swagger that marked George W. Bush’s presidency, vowing to install a no-fly zone over Syria even over the objections of Moscow, which has sent its planes into the skies over the country’s vicious civil war in support of the government in Damascus.

“We would shoot down the planes of Russian pilots if in fact they were stupid enough to think that this president was the same feckless weakling (as) the president we have in the Oval Office … right now,” Christie said.

Kentucky Sen. Rand Paul – emblematic of a more restrained brand of foreign policy – hit back: “I think if you’re in favor of World War III, you have your candidate.”

No national foreign policy road map

The contentious exchanges not only reflected the staggering array of international challenges that will confront the next president but revealed the lack of a national political road map on foreign policy akin to that which helped sustain the United States throughout the Cold War.

They also exposed fault lines at the center of the Republican Party, deepened by more than a decade of conflict abroad, that have often poisoned the political well in Washington and which mirror disputes about intervention abroad also raging between Hillary Clinton and Bernie Sanders in the Democratic primary.

In the Republican debate on Tuesday, unresolved disputes left candidates on the opposite sides of lines drawn between neoconservative and isolationist foreign policy approaches, and between a idealistic vision of American power where the United States helps those yearning for freedom and a world view rooted in realpolitik in which overthrowing dictators sparks chaos.

The party has yet to make a final decision on whether America is most secure with robust interventions abroad or with the more targeted operations preferred by the Obama administration, which has made strenuous efforts to avoid being sucked back into the volatile region.

But the discussion was a sign that the questions on applying U.S. military power and the extent to which Americans must cede freedom at home will not, as Obama once hoped, be resolved in his tenure.

In fact, with the rise of ISIS and the splintering of the map of the Middle East, it’s now clear that the war on terror that George W. Bush once said would end at a time of America’s choosing, will shape a third successive presidency regardless of who wins next year.

Each school of foreign policy thought vying for prominence in the Republican Party had a candidate in the CNN debate.

In one corner was Florida Sen. Marco Rubio, who is promising a proactive, aggressive American foreign policy with a moral underpinning and military buildup akin to Ronald Reagan while declaring that great powers such as Russia and China are clear adversaries.

Cruz vs. Rubio

In one of a clutch of clashes with Texas Sen. Ted Cruz, Rubio chided his Senate colleague for voting to reform the National Security Agency’s phone data surveillance program, which he said was needed more than ever, thanks to the rise of ISIS.

“It is the most sophisticated terror threat we have ever faced. We are now at a time when we need more tools, not less,” Rubio said.

Cruz hit back by linking Rubio to Clinton and Obama with the 2011 toppling of Libyan strongman Moammar Gadhafi, which bred instability and a haven for the terror group. He also faulted the administration for deserting Egyptian President Hosni Mubarak, a close U.S. ally who was overthrown in the Arab Spring.

“(Bashar al-) Assad is a bad man. Gadhafi was a bad man. Mubarak had a terrible human rights record. But they were assisting us – at least Gadhafi and Mubarak – in fighting radical Islamic terrorists,” Cruz said. “If we topple Assad, the result will be ISIS will take over Syria, and it will worsen U.S. national security interests.”

READ: Watching the GOP debate through Muslim eyes

But Cruz did not go as far as Paul, his sometimes ally on the right in the Senate, in his opposition to American military involvement abroad.

Cruz vowed to “carpet bomb” ISIS and called for robust Pentagon spending.

Indeed, the varied views on just about every national security issue thrown at the candidates exposed the extent of the lack of a unified foreign policy vision in the GOP, once a bedrock of the Republican brand.

Trump, the billionaire real estate mogul now leading the pack according to polls, endorsed strong-arm tactics such as killing terrorists’ family members and shutting down parts of the Internet used by terror groups. Be he also offered a soliloquy on the waste of spending billions of dollars toppling dictators – an apparent reference to Iraq – as opposed to domestic needs such as schools, hospitals and roads.

That assertion earned a sharp rebuke from former businesswoman Carly Fiorina, who told him, “That is exactly what President Obama said. I’m amazed to hear that from a Republican presidential candidate.”

Trump under fire

Trump also came under attack from former Florida Gov. Jeb Bush, who dismissed the reality TV star’s policies as hewn from Saturday morning cartoons.

This is not a serious proposal,” Bush said of Trump’s call for a temporary ban on Muslims entering the United States. “In fact, it will push the Muslim world, the Arab world away from us at a time when we need to reengage with them to be able to create a strategy to destroy ISIS.”

Trump retaliated by telling Bush his misfiring campaign was a “disaster,” but his lack of experience inadvertently came out in his answer to a question about the U.S. nuclear “triad” – a deterrent of weapons launched from the air, land and sea.

“Nuclear changes the whole ball game,” Trump said, apparently believing he was being asked about the chances of terrorists getting weapons of mass destruction.

The situation was tailor-made for Rubio to show his smarts, and to implicitly make the case that foreign policy experience is vital in the coming election.

“First, let’s explain to people at home … what the triad is,” Rubio said, in an answer that deftly exacerbated Trump’s embarrassment.

But Trump was not the only one to slip up. Christie vowed to stand strong with Jordan’s King Hussein – who has been dead for 16 years.

It’s not yet clear how GOP voters will evaluate such slips as they increasingly focus on national security. Terrorism topped the list of voter concerns in a recent New York Times poll, eclipsing the economy, which had long been in the first slot.

The new primacy of foreign policy in the campaign helps explain why retired neurosurgeon Ben Carson has slipped from his spot near the top of polls in the wake of deadly terror attacks in Paris and San Bernardino, California, as he has faltered when facing national security questions.

But Trump, who has no more elected experience, has surged in polls as he has harshly called out the terrorists and blasted Obama’s policies.

Yet there is some evidence to suggest GOP voters are less eager for experience of the type offered by candidates like Bush than the outspoken projections of strength embodied by Trump.

A New York Times/CBS News poll this month showed that 71% of Republican primary voters are very or somewhat confident in Trump’s ability to handle terrorism. The corresponding figure for Bush was 53%.

And polling from the Pew Research Center released in October shows that whatever their views on experience, Republican primary voters are preoccupied by national security. Republicans are 15 percentage points more likely than Democrats to consider terrorism as very important and 12 points more likely to view foreign policy that way.

For now, the only unifying pillar for Republicans is their agreement that Obama has done a terrible job. But it remains to be seen what new policy direction GOP voters will back as they head to the polls in just a few weeks.