If you're still hoping to see a serious foreign-policy debate between Mitt Romney and President Obama, you'll have your chance tonight, when the candidates will focus on global issues.

Don't get your hopes up, however. For one thing, the two men know the public isn't focused on foreign affairs. For another, the most serious security challenges confronting the country -- in the Mideast and South Asia -- are so complex and fluid, it's hard to provide clear answers. This makes for a lot of posturing by Romney (it's easier for a challenger to insist the answers are obvious) and for oversimplification by Obama.

In the hope that tonight's moderator, Bob Schieffer, can prod the two men to candor, here's what I'd like to see them address:

First, enough already about the attack on our mission in Benghazi, Libya. Amazingly, this was one of only two foreign-policy questions at last week's debate. (The other, on China, elicited routine Beijing-bashing by both men.) The Benghazi attack is not the most pressing national security question that confronts us. Issues of diplomatic security fall under the purview of midlevel State Department bureaucrats, not the White House. Secretary of State Hillary Rodham Clinton has taken responsibility for any security failures -- but so should Republicans who voted to cut the budget for future embassy security needs.

Instead, could we please hear a serious discussion of how to deal with new Islamic realities after the Arab Spring? Romney argues that the Islamists emerged because Obama didn't sufficiently support democratic forces in the region. But, a bit belatedly, Obama did back Tunisian, Egyptian and Yemeni rebels in their struggle. Once their dictators fell, their publics voted Islamists into office, with hard-line Salafis on the margins. Nothing Washington did could have made those elections turn out the way we hoped.

So let's have a discussion: Should the United States support Arab rebellions wherever they lead? Should it support Arab democracy if voters choose governments we don't like? Would Romney repudiate Islamic governments that won legitimate elections? Will Obama (or Romney) cut off aid to an Islamic government in Egypt if it represses women and minorities? What if that Egyptian government then threatens to abrogate its peace treaty with Israel?

And let's have an honest discussion about Syria, whose sectarian civil war is poisoning the region. Obama is holding back, letting the Arab Gulf states provide Syrian rebels with light (and inadequate) weapons.

Romney chastises the president for timidity on Syria, yet differs little: He would only urge the Saudis and Qataris to provide heavier arms to "good" rebels. However, outsourcing this effort is risky: The Gulf states are more likely to aid the Islamists. What happened to Romney's "leading from the front"?

The candidates should tell us how they would choose between two bad options: Would they let the sectarian war continue, even if it spreads all over the region? Assist Syrian rebels who may well turn against us?

And on to Iran. Obama says he'll prevent Iran from getting a nuclear weapon. Romney says he'll prevent Tehran from getting the "capacity" to build a weapon. Capacity means the production of sufficient fissile material that Iran, in theory, could further enrich to bomb-grade capacity and, ultimately, attach to a weapon (which also takes time to design). Capacity is also the red line used by Israeli leader Benjamin Netanyahu, who says Iran will acquire it within six months.

Does Romney really mean he'd go to war next spring, on Netanyahu's schedule? Would he really immerse the United States in another Mideast conflict in his first term? As for Obama, how will he know when Iran is on the verge of getting a weapon?

And is Iran -- whose economy is reeling from Obama's sanctions -- really the greatest security threat the United States faces? What about Pakistan, which is permeated with Islamist terrorists and has dozens of nuclear bombs?

This brings us to the 11-year-old war in Afghanistan, a subject both candidates are pretty much avoiding. Joe Biden said in the vice presidential debate that "we are leaving in 2014, period." His sparring partner, Republican Paul Ryan, concurred on that date.

Yet everyone knows the war is going badly. Despite Romney's hints that he might slow the withdrawal, the American public wants this war to end.

Whatever the weaknesses of Obama on these issues, I've heard no clear alternatives from Romney, and no recognition of the global changes of the last decade. I hope Schieffer will press both candidates for real, not canned, answers. But my expectations aren't high.