Tomorrow night’s debate in South Carolina will focus on foreign policy. It’s supposed to be 90 minutes, but CBS will only broadcast the first hour nationally. It’s not clear how many viewers will watch on Saturday, let alone get to see the final 30 minutes. (The final half-hour will be broadcast on Sunday on “Face the Nation.” CBS will show portions of the final half-hour on its Sunday-morning show “Face the Nation.”)

Suffice it to say, the foreign policy debate on Nov. 22 hosted by the American Enterprise Institute and the Heritage Foundation may be a more intense and serious test of the candidates’ foreign policy knowledge and vision. But if nothing else, South Carolina’s outing gives the candidates some much needed practice in fielding national security questions.

Foreign policy has been badly neglected in the campaign, and a debate on the topic is long overdue. The terrain is perilous for those who don’t have a clue what they are talking about and haven’t spent much time on national security matters, let alone reading newspapers. I have in mind, specifically, Herman Cain, who seems to delight in not knowing anything about a critical part of the job he wants to hold.

There are two defenses for candidates inexperienced in foreign policy matters. The first is that they know how to get good advisers. Needless to say, Cain’s judgment in hiring staff is atrocious, so his promise to “consult with his staff” is not comforting to many voters. The second defense is that so long as your “instincts” are good and you understand generally America’s role in the world you’ll do fine as commander in chief. This latter argument has some intuitive appeal, especially since we currently have a president whose foreign policy flubs are traceable to his cramped view of American leadership and his lack of faith in America’s ability to be a force for good in the world.

But in practice, instincts that aren’t grounded in experience or knowledge are often faulty. And the danger that a president will project weakness, ignorance or uncertainty on the international stage shouldn’t be underestimated. Ideally, you would want someone who has a solid working knowledge of our national security challenges and faith in America’s ability to project strength, foster liberty and keep the peace. The choice, at least not yet, is not between our current commander in chief and an ignoramus; Republicans have the chance to select a nominee whose vision, values and intellect are most likely to result in a coherent and effective foreign policy.

It wouldn’t be fair, and indeed it would be waste of time, to turn this into a geography bee or quiz on world leaders. However, it is important to know in general terms, for example, what the candidates think of defense spending, if they regard Russian reset as a failure or success, how they would treat human rights and what principles would guide them in shaping Middle East policy. It would be nice to know what role they think international bodies (NATO, the United Nations) can play and how they intend to manage our relationship with China.

Earlier this fall Mitt Romney put out an impressive white paper and gave a speech outlining his views. From conservative foreign policy gurus he generally got strong reviews, most especially for his conviction that we need to maintain adequate spending for national security. The danger for him in these debates is when he tries to qualify, shade or add more nuance than is needed. Short declarative sentences on his goals and means of achieving them would aid in convincing voters that he’s resolute on foreign policy.

Cain certainly has the most to lose here. He’s made gaffes on everything from China’s nuclear capability to his willingness to trade Gitmo detainees if an American were captured. His crack about “Ubeki-beki-beki-beki- stan-stan” suggests a dangerous level of know-nothingness. Frankly, it will be remarkable if he can formulate any substantive response (“I’ll talk to my advisers” doesn’t qualify). The evening is fraught with peril for him.

Newt Gingrich’s problem is not a lack of specific knowledge but an overabundance of facts and notions, not all of which are true or well-reasoned. He fancies himself a historian and big thinker, but he needs to show he’s grounded and stable, in the same way that Ronald Reagan had to convince voters he wasn’t a crazy man who’d start a nuclear war. Temperament has never been Gingrich’s strong suit, but it’s critical in projecting the image of a credible commander in chief.

Texas Gov. Rick Perry seems to treat his military experience as top secret. He doesn’t talk much about it, doesn’t refer to many specifics and doesn’t tell us how it relates to his world view. This is a terrible error. After all, he’s the only one with actual military experience. That counts for quite a lot. He’d be wise to draw on that experience and try to project a level of gravitas that others may lack. He got himself into trouble in an earlier debate trying to answer a question on Pakistan. The lack of familiarity with various issues is a real concern, but rather than try to fake his way through an answer like a kid delivering a book report on something he never read, he’d be wise to back off the particulars and tell the audience what will guide his decision-making.

Rick Santorum has real experience in foreign policy, helped craft an early Iran sanctions bill and can speak in an informed way on a number of international hot spots. He’s dangerous in the debate because he can call out his opponents’ errors and misstatements. His challenge is always to seem presidential and avoid complaining about lack of recognition for his past service and lack of face time in the debate.

All candidates would be wise to keep in mind a few things. First, “I’ll defer to the generals” is not a good answer. A commander in chief wants to consult with his military and civilian advisers, but critical decisions on war and peace, on troop pullouts, on end dates and the like are the president’s responsibility. If not for President George W. Bush overruling his advisers, we wouldn’t have had the surge in Iraq and a good outcome.

Second, they should avoid the temptation to pander to the penny-pinchers. National security is the first obligation of government, and they shouldn’t be shy about saying we need to fund it adequately.

And finally, they’d do well to resist the temptation, as great as it may be, to criticize everything President Obama has done. We have killed Osama bin Laden. Moammar Gaddafi is dead. It’s fine to critique how we got into Libya or his politically imposed deadlines on Afghanistan, but it would speak well of the candidates to give credit where credit is due. They needn’t worry; Obama’s list of “successes” is short.

Right Turn will have a wrapup and analysis of the debate over the weekend.

UPDATE (12:40 p.m.) :A CBS spokesman emails to say that no, the final half hour of the debate won’t be broadcast on Face the Nation. Just ”additional portions” of the debate will be shown on the CBS Sunday talk show. The entire debate will be viewable at NationalJournal. com and CBS.com. Some CBS affiliates will carry the entire debate.