When Chris Christie did the Full Rudy the other day - as in, Giuliani; as in, playing the 9/11 card - it appeared at first that he was merely staking out turf as a national security hawk, with his eye on 2016. But he wasn't just playing politics. He was taking sides in a vicious GOP clash over how best to wage the war on terrorism.

At stake is not only the party's identity - or, in contemporary parlance, its "brand" - but perhaps its political viability as a steward of foreign policy.

Brit Hume, the conservative commentator, said it well on Fox News yesterday: "This is a battle that is real within the Republican party. It is a strong and deep disagreement between internationalists, and those who are in some way have been labeled isolationists. It has been going on for a long time. It has subsided for periods of time. And now it’s back. The party is going to have to have this out."

Christie waded in last Thursday night, at a policy retreat in Colorado. He was ticked that the House of Representatives had nearly passed an amendment to defund the National Security Agency's phone data collection program. He was doubly ticked that 94 House Republicans (41 percent of the GOP caucus) had voted thumbs down on the NSA. And he's ticked that the GOP's small-government libertarian movement seems to be growing, under the tutlage of Senator Rand Paul - a potential rival in 2016.

Referring to the NSA vote, and to Paul's frequent attacks on the government's domestic surveillance, Christie grumbled: "This strain of libertarianism that's going through parties right now and making big headlines is a very dangerous thought....These esoteric, intellectual debates - I want them to come to New Jersey and sit across from the widows and the orphans and have that conversation. And they won’t, because that’s a much tougher conversation to have."

Christie wasn't done: "As a former prosecutor who was appointed by George W. Bush on Sept. 10, 2001, I just want us to be very cautious. What we as a country have to decide is, do we have amnesia? Because I don't. I remember what we felt like on Sept. 12, 2001....The next attack that comes, that kills thousands of Americans as a result, people are going to be looking back on the people having this intellectual debate and wondering whether they put - " whereupon, Christie shut himself down.

Politics and policy

On one level, this was pre-'16 gamesmanship. The Republican field is wide open, and the party establishment (foreign policy wise men, big donors) are looking for a national security hawk who can sustain the party's traditional tough-on-terrorists image. Rudy Giuliani tried to fill that niche in the '08 primaries, offering himself as a kickass northeasterner who could potentially put that region in the Republican column. It's no coincidence that some of Rudy's '08 campaign aides are now working for Christie.

Plus, going hawkish on national security - embracing NSA surveillance, endorsing the hypervigilant Bush-Cheney ethos - might help Christie woo some of the conservative primary voters who got mad in the aftermath of Hurricane Sandy, when Christie dared breathe the same salt air as President Obama.

But this is about policy as well as politics. The interventionists have controlled GOP foreign policy ever since Dwight Eisenhower defeated conservative isolationist Robert Taft for the presidential nomination back in 1952. Between 1968 and 1988, Republicans won five of six elections in part because they were perceived to be tougher on America's enemies.

But today's GOP interventionists fear that Rand Paul and his ascendant libertarian allies will wreck the party brand; that by arguing for a reduced American commitment abroad and less vigilant surveillance at home, Paul and company will force the GOP to cede the foreign policy center to the Democrats (more specifically, to Hillary Clinton) in 2016.

Another northeastern Republican, New York congressman Peter King, echoed Christie yesterday on CNN: "The overriding concern here has to be national defense, national security, and not be apologizing for America." (The latter phrase is noteworthy; Republicans far more typically accuse liberals of "apologizing for America.") Last week, King was more explicit, stating in a press interview, "I don't want Rand Paul to be the face of the Republican party." He and others believe - with reason - that Paul libertarianism would trigger a 2016 wipeout, a la Barry Goldwater's GOP debacle in 1964 and George McGovern's Democratic debacle in 1972.

Christie under fire

Indeed, when Paul said in speech last week that "we should never be a nation that is eager to get involved in civil wars that don't affect our national security," and that "America's mission should always be to keep the peace, not police the world," those sentences could have been lifted verbatim from McGovern's losing "Come Home America" campaign.

But he's certainly not cowed by his critics. As soon as Christie swiped at him, it was game on.

Paul's office quickly retaliated: "If Gov. Christie believes the constitutional rights and the privacy of all Americans is 'esoteric,' he either needs a new dictionary, or he needs to talk to more Americans, because a great number of them are concerned abut the dramatic overreach of our government." (Message to conservative primary voters:  Christie is just another big-government guy.)

But this Twitter counterattack, on Paul's campaign feed, was more insidious: "Chris (Crist)ie should hear from more Americans who value both security and privacy" and "Chris (Crist)ie thinks freedom is dangerous." Note the deliberate misspelling, and the punctuation, of Christie's surname. Paul was clearly invoking Charlie Crist, the moderate Republican governor of Florida who was driven out of the party by the conservative base - and suggesting that the base should similarly kick out Christie.

As Brit Hume said on Fox News, "The party is going to have to have this out." The having has already begun. And if Christie and Paul share the presidential debate stage, pop that popcorn.

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