Whether the issue is gun control, energy policy or civil liberties, Republican John McCain and Democrat Barack Obama seem to be on the hunt for opportunities to draw contrasts with one another.

Well, there is one area of public policy where the differences between these two men could not be more pronounced. So you would think that the candidates would jump at the chance to talk about it.

Not at all. Perhaps that is because this particular issue is so messy and so explosive that, no matter which candidate brings it up, there is the potential for blowback. It's also one of those complicated issues with no good options, only tripwire and trapdoors.

And so neither McCain nor Obama is in much of a hurry to begin a long and detailed debate on the subject. They make comments here and there, but there is no sustained dialogue.

That is unfortunate. There are few issues of greater consequence in this election than the Iraq war and what the next president intends to do about it. At first glance, you might think the answer is rather obvious. McCain has been a strong supporter of the war, often willing to stand alone even within his own party. He has even dished out some of his trademark straight talk to voters about how there may be a need for a long-term troop presence in Iraq. Meanwhile, Obama likes to brag to leftist anti-war groups about the vote he wasn't around to cast in 2003 and remind people that, while still in the Illinois State Senate, he gave a speech against the war.

But running for president is one thing, serving as president is another. Either of these men could be headed for a reality check if elected. If McCain is the next president, he will have to acknowledge that current troop strength cannot be sustained indefinitely and that the majority of Americans want out of Iraq. If Obama is elected, he'll have to cool his plans for an immediate withdrawal or risk that Iraq will descend into chaos and fall into the clutches of Iran. The candidates should start talking more about Iraq and let voters know what they would do to ensure victory and bring our troops home. This might be politically risky, but it's also necessary. The American people, who time and again send sons and daughters off to war, deserve no less.

This issue is more complex than you would imagine from listening to the slogans and sound bites that come from special-interest groups. For instance, MoveOn.org is airing a repulsive and wildly unfair television ad featuring a young mother holding her baby, Alex, and telling John McCain she won't allow him to draft the toddler to help secure victory in Iraq. It is just as well since the little guy doesn't really seem battle-ready as of yet.

These stunts may help fringe groups get attention but they only confuse and inflame the public. They make the toughest issues seem cut and dried. They aren't. And the Iraq war certainly isn't.

No one knows that better than the men seeking the White House. All the more reason they should explain exactly what they'll do if they get there.

Reprinted from The San Diego Union-Tribune.