When five American soldiers were killed at an Iraqi government building in Karbala in January, Democratic Sens. Chris Dodd and John Kerry erupted in outrage. They both knew one of the soldiers killed, a talented West Point grad. According to The Washington Post, his loss "radicalized Dodd, energized Kerry and girded the ever-more confrontational stance of Democrats in the Senate."

It turned out that Iran's Quds Force helped carry out the attack, providing training to the Shiite group responsible for it. So, the Iranians had effectively killed those Americans, but Dodd and Kerry have yet to become notably energized or radicalized about counter-acting Iran's malign influence in Iraq.

Democrats angered at American casualties in Iraq can't summon more than pro forma denunciations of one of the main forces responsible for them. It's the Iran exception: Because our intelligence on Saddam Hussein's weapons was flawed and the Iraq War devilishly hard, Iran has practically carte blanche from half the American political spectrum to develop a nuclear weapon, kill Americans in Iraq, pledge to wipe a nearby country off the map, arm dangerous militants throughout the region and take Westerners hostage.

These Iranian depredations usually evoke a steely Democratic resolve -- to oppose whatever measures that the Bush administration might be contemplating in response. Sen. Dodd, a Democratic candidate for president (if you hadn't noticed), wrote President Bush a letter a few days ago complaining about "increasingly bellicose public statements by United States officials." What was this reckless saber rattling?

It's hard to know. U.S. military officials have said that three-quarters of the attacks on our troops in Baghdad have been launched by Iranian-linked Shia militiamen. Maybe they are supposed to let these acts of war pass unremarked? Meanwhile, State Department spokesman Sean McCormack has been saying that "we're working on the elements of a resolution" for further sanctions on Iran, pending "ongoing discussions."

Scary stuff, no? It's hardly the equivalent of "Death to America," which Iranian President Mahmoud Ahmadinejad shouts at rallies in Iran.

Dodd and other Democrats call for "robust" diplomacy to deal with Iran. But Ambassador to Iraq Ryan Crocker already has held meetings with Iranian officials to urge them to stop arming Shia militants with deadly, explosively formed penetrators. Iran has only been sending more munitions to Iraq. For her part, Secretary of State Condoleezza Rice broke with decades of U.S. policy to offer to negotiate directly with the Iranians -- together with our European partners -- if they would suspend their uranium enrichment. The Iranians have since boasted of spinning 3,000 centrifuges.

Liberals like to say of the Bush administration's allegedly militaristic foreign policy that if the only tool you have is a hammer, every problem looks like a nail. Likewise, if the only tool you have is dialogue, everyone looks like a reasonable interlocutor.

So it is that Columbia University could invite Iranian President Ahmadinejad to come speak on campus for, as President Lee Bollinger put it, "academic purposes." As if Ahmadinejad were merely a vehement participant in the graduate seminar "Jews and Arabs: Approaches Toward a Problem." The Iranian inevitably blustered and lied, and probably enjoyed the legitimacy conferred by the visit, even if Bollinger did scold him.

In the aftermath of the Vietnam War, the Democratic Party's foreign-policy views curdled from the expansive vision of John F. Kennedy to an inward-looking disposition tinged with paranoia about our own government. The Iraq War has had the same effect on Democrats, many of whom seem to consider the Bush administration a greater threat to peace than the mullahs in Iran. Can you imagine MoveOn.org ever attacking Ahmadinejad in a full-page New York Times ad, let alone as harshly as it denounced Gen. David Petraeus?

Out in the real world, Iran is a deadly enemy of the United States. Diplomacy might change its behavior, but only if backed by serious sanctions, and perhaps the credible threat of force. That's the hard reality. The Iran exception cannot stand.