One of the sound-bites being paraded around is on whether particular Democratic candidates are “credible” on national security. The latest iteration of this theme was expressed by Joe Biden, who said:

[T]he candidates have to “demonstrate that they have a foreign policy, a security policy, that is coherent and is grown up, that we can handle the bad things out there in the world.”

But what is credibility? In this voter’s mind, it’s not strictly speaking about Iraq: by my standard, you could be credible but have opposed the war in Iraq. To me, I think credibility boils down to whether or not the candidate believes that other countries get to veto the use of American military power to achieve an objective that is in the national interest. Ultimately, this question—not the war question—is where many of the Democratic candidates lose their credibility with me.

This is not, mind you, a call for blanket unilateralism. When other countries share our objectives, and are willing to cooperate with us in achieving those objectives, we can and should work with them to do so. But when other countries clearly have different objectives than those of the United States—as was the case in the Iraq war, where a number of middle-power states wanted to pursue commercial ties with the Saddam regime and were plainly unwilling to commit their own resources to containing that regime’s ambitions for rearmament and obtaining non-conventional weapons—an American president would be deeply unwise to allow them to decide whether and how American military force should be used.