So now Barack Obama has come out swinging against Hillary Clinton. After months of gentlemanly restraint, he accuses her of poll-tested, triangulated dissembling. It’s true that Clinton has ducked questions on Social Security reform and abandoned her husband’s principled commitment to free trade. But the Obama attack deserves to fail. On the big foreign policy questions of the day, it is Mr. Obama who looks craven and Mrs. Clinton who looks honest.

Begin with the Iran debate. All the Democratic presidential hopefuls know that a nuclear Iran is scary. They know that the Europeans have been patiently negotiating with Iran to secure a freeze of its program and that the Iranians have been stalling. But Mrs. Clinton is the only Democratic candidate who unequivocally embraces the obvious next step: Push hard for the sanctions that might change Iran’s calculations. Unlike all her opponents, Mrs. Clinton supported a pro-sanctions resolution in the Senate. Ever since that vote, Mr. Obama and the rest have attacked her mercilessly.

It’s not that Mrs. Clinton’s rivals believe sanctions are mistaken. It’s that they lack the courage to defy Bush-hating primary voters, who think that lining up with the president on any issue is like becoming a Death Eater. “I learned a clear lesson from the lead-up to the Iraq war in 2002,” says base-pleasing John Edwards, “if you give this president an inch, he will take a mile — and launch a war.” “This is a lesson that I think Senator Clinton and others should have learned,” Mr. Obama echoes. “You can’t give this president a blank check and then act surprised when he cashes it.”

The truth is that Mrs. Clinton did not give Mr. Bush any sort of “blank check” — if President Bush wants to bomb Iran or hit Iranian units inside Iraq, he can do so without a Senate resolution. But Messrs. Obama and Edwards are so intent on Bush-bashing that they refuse to cut him any slack, even when he advances a policy that they might ordinarily favor.

After the administration announced a new package of Iran sanctions on Thursday, Mr. Edwards declared that the president and his team had once again “rattled their sabers in their march toward military action.” Bush hatred has driven him to the point where he regards sanctions as a harbinger of war rather than an alternative.

Mrs. Clinton’s rivals are contemplating history and deriving only a narrow lesson about Mr. Bush: Don’t trust him when he confronts a Muslim country. But the larger, more durable lesson from Iraq is that wars can be caused by a lack of confrontation. The Iraq invasion happened partly because the world had lost the stomach to confront Saddam Hussein by other means.

By 2002, the sanctions on Saddam Hussein’s regime had been diluted, and there was pressure to weaken them further. Saddam was no longer “in his box,” to use the language of the time: If you believed that a resurgent Saddam Hussein presented an intolerable threat, it was worth taking the risk of unseating him by force, sooner rather than later. Alone among the Democratic candidates, Mrs. Clinton has the honesty to insist that the case for war was reasonable at the time — even if, with the benefit of hindsight, the invasion has proved disastrous. In sticking to that politically difficult position, Mrs. Clinton is saying that, despite its awful risks, war can sometimes be the least bad choice. She is not running away from military power, even in a political climate that makes running attractive.

Likewise on sanctions, Mrs. Clinton is the only one to insist that sanctions are less a prelude to war than a means of forestalling it. They are more likely to work, moreover, if the military option is looming in the background, which is why bellicose comments from Mr. Bush or his vice president don’t prove that war is the preordained strategy.

The idea that the threat of war can prevent actual war is the most basic lesson of nuclear doctrine, but it appears to escape the Bush haters. In a recent interview with NPR, Mr. Obama argued that Iran understands America’s power, so there is no need to advertise it further. If the Bush administration’s central error has been to rely too much on military force, the Bush haters’ mistake may be to shrink from all mention of it. Mr. Bush’s record is disastrous, and on an emotional level, Bush hatred is understandable. But what we need in the next president is a vision of the world that’s not distorted by the bitterness of recent times: a vision that accepts the limits of military force but also acknowledges that Americans face real threats, that feckless foreign powers can sometimes make the ideal of multilateralism unattainable and that war can sometimes be the least bad option.

Mr. Obama, who promised to rise above partisanship, seems too fearful of his party’s Bush-hating base to offer that vision. It’s impressive and surprising that Mrs. Clinton, who railed against a vast right-wing conspiracy not so long ago, has risen above Bush hatred in forming her worldview. She has come a long way in just one decade.

Mr. Mallaby is a fellow for International Economics with the Council on Foreign Relations.