I suspect few readers will disagree when I say that not one of the presidential candidates, Republican or Democratic, has yet articulated a compelling campaign theme. All favor security. Not one opposes prosperity. Each promises to protect Social Security and improve health care. Voters can be forgiven if they are not overwhelmed.

Let me offer a different approach on the off-chance that some candidate might find it useful: Tell voters the hard truth – and challenge them.

In particular, tell them we are at a critical moment in our nation's history: A dangerous enemy is waging an unconventional war against us. We are just beginning to learn how to defend ourselves. Remind them that this enemy has been underestimated by presidents and lawmakers of both parties many times, over many years.

Tell them, too, that fighting this enemy is a burden that history is asking the current generation of Americans to bear. We must do this for future generations – as past generations fought for us.

Say frankly that if we don't have the stomach for a long and difficult war, we will be defeated by movements that are more determined than we are -- and more ruthless than we can ever imagine becoming.

It is rare for politicians to talk this way. But it is not unprecedented. In 1940, Hitler's armies were wiping off the map one European nation after another. In Britain, many people believed the wisest course was not to fight the Nazis but to negotiate a diplomatic settlement, to address the legitimate grievances of the German people.

On May 13, 1940 Winston Churchill entered the House of Commons for the first time as British Prime Minister. Next to him was Neville Chamberlain, the outgoing PM. Chamberlain was greeted with cheers. Churchill was not.

Churchill didn't tell the officials and the public what they wanted to hear. He told them what they needed to hear: that it would be both wrong and unproductive to attempt to appease tyrants.

He famously said: "I have nothing to offer but blood, toil, tears, and sweat. We have before us an ordeal of the most grievous kind. We have before us many, many months of struggle and suffering."

It is possible the current conflict will be less lethal than World War II. But it will last longer -- it already has. What policy would a Churchillian presidential candidate adopt? Churchill said: "You ask, what is our policy? I say it is to wage war by land, sea, and air. War with all our might and with all the strength God has given us, and to wage war against a monstrous tyranny never surpassed in the dark and lamentable catalogue of human crime. That is our policy."

Any candidate supporting this approach would have only disdain for such groups as MoveOn.org which this week accused General David Petraeus of "betrayal" for refusing to accept defeat in the Battle of Iraq

After Gen. Petraeus' initial testimony, both the Washington Post and the Washington Times headlined his support for troop reductions next year. But, by definition, a "surge" subsides. Petraeus has always intended to transfer responsibility for security to Iraqis – he just wants to decide when and where, based on conditions on the ground, not legislation passed in Washington.

The New York Times, whose editorial page views are hardly distinguishable from those of MoveOn.org, was closer to identifying the news in Petraeus' report. Its top story: "Petraeus Warns Against Quick Pullback in Iraq." It should not require a Churchill to see that if American forces leave Iraq precipitously, America's enemies will fill the vacuum. And Iraqis who have been fighting with us will be slaughtered. People around the world will get the joke: To be America's friend is more perilous than to be America's enemy.

The real news in Petraeus' testimony: Americans troops have been beating al-Qaeda in Iraq and, as that job gets done, it is Iranian-backed militias that are becoming the main problem that needs to be eliminated. The regime in Tehran wants Iraq as its colony. It doesn't want Iraq to be an America ally in the war with Militant Islamism.

On several occasions over the past three decades, Tehran has sent murderers to kill Americans. On none of those occasion has the United States responded forcefully. The mullahs are betting there will be no break with that precedent – not by the current occupant of the Oval Office and not by whoever replaces him in 2009.

I suspect more than a few Americans would vote for a candidate who tells us the mullahs are dead wrong.