Herman Cain is no foreign policy maven.

Republican presidential candidate businessman Herman Cain speaks with the media after a interview on NBC's Meet the Press at NBC studio in Washington on Sunday, Oct. 16, 2011. (AP Photo/Jose Luis Magana)

Pressed on the issue, Cain added: “If, if it’s an act of war, and the evidence suggests that, then I am going to consult with my advisers and say, ‘What are our options?’”

The leading 2012 GOP presidential contender also seemed not to know what a “neoconservative” was and offered a halting — though ultimately decent — answer on American policy toward Afghanistan.

Cain’s lack of detailed answers on foreign policy matters have not hurt him in the GOP presidential primary thus far for three reasons: 1) the Republican electorate is almost exclusively focused on the economy; 2) his candor is part and parcel of his “not a politician” appeal; 3) in a crowded Republican field, he’s been able to mask what he doesn’t know easily and effectively.

Though he has skimped on the details of his foreign policy advisers in debates, he named mentors in his “Meet” appearance, including former Bush U.S. Ambassador to the United Nations John Bolton, former Nixon Secretary of State and former Reagan deputy secretary of defense and current Fox News analyst Kathleen McFarland.

And, as we have written many times in this space, foreign policy is — in its best days — a lower first-tier issue for voters. In times of economic uncertainty, it’s barely even considered.

In the latest Washington Post-ABC News national poll, just 1 percent of Republican respondents named foreign policy as the most important issue facing the country. By contrast, 51 percent named the economy.

But, while people may not vote on “foreign policy” per se, a working knowledge of the world stage — and America’s role in it, is, without question, regarded as essential by the public.

That is, people may not care all that much about the war in Afghanistan or Iraq, but they damn well expect that the person they are electing knows enough about it to keep them safe from harm.

(Remember that one of President Obama’s signature lines is that his first job as commander-in-chief is to keep the American public safe.)

“Being commander in chief is the most important role for any president and Herman Cain just isn’t credible in that role,” said Max Boot, a senior fellow at the Council on Foreign Relations and a former foreign policy adviser to Arizona Sen. John McCain’s (R) 2008 presidential campaign. “National security knowledge isn’t enough to win the presidency as McCain showed, but it’s lack can be fatal.”

To be fair to Cain, as recently as a month ago he was an also-ran in the 2012 presidential sweepstakes, regarded as an able speaker but not given any real chance of becoming the Republican presidential nominee.

With his rapid rise, however, comes increased scrutiny on what he knows and, just as importantly, what he doesn’t.

So, while the 9-9-9 tax reform plan and his own personal charisma may have been enough to lift him from afterthought to top-tier candidate, they aren’t enough to keep him in that pole position unless Cain can demonstrate a broader readiness to assume all of the responsibilities of being president.

“Cain needs to do more so he doesn’t alarm voters by a glaring lack of knowledge or interest,” said Ed Rogers, a longtime Republican strategist not affiliated with any of the current candidates.

The challenges for Cain as he attempts to transform himself into a serious contender for the Republican nomination are many and varied. But there may be none as important as demonstrating to the public that he is up to the job. And that means boning up a bit on foreign policy matters. And fast.

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