Since the debate, the right-leaning blogs (e.g. Tacitus) have latched on to Kerry's "error" of saying: "You talk about mixed messages. We're telling other people, "You can't have nuclear weapons," but we're pursuing a new nuclear weapon that we might even contemplate using. Not this president. I'm going to shut that program down, and we're going to make it clear to the world we're serious about containing nuclear proliferation."
They make it clear that they think this is both a political blunder (i.e. most Americans watching the debate will disagree with him), and a substantial blunder (i.e. Kerry is just plain wrong on this issue).
I have no idea if what Kerry said was a political blunder as I have no idea what most American's think about the US developing "Bunker Buster" nukes, but I do have to say that the right-leaning blogs are wrong on their second point; Kerry is dead right when it comes to the susbtance of the issue.
[Note: edited to correct spelling mistakes.]
First off, the point he was trying to make was about hypocricy. Namely, he was pointing out that prohibiting other countries from developing new nuclear weapons while at the same time developing new nuclear weapons ourselves is flat-out hypocricy. So Kerry is sending a "ending nuclear proliferation starts at home" kind of message. Though you can certainly argue that there are good reasons why one country should be able to develop new neclear weapons while others can't, Kerry's position is hardly a bad one and is certainly not wrong in any sort of obvious way.
Secondly, by making this statement he shows that he knows the history of the development of nuclear weapons. During the Cold War, war strategists and weapons researchers alike quickly recognized that any "limited" use of nuclear weapons would quickly escalate into all-out nuclear war and Mutual Assured Destruction. There would never just be a nuclear battle. There could only be full-on nuclear war and MAD. So the strategists and researchers came to a tacit agreement: make the bombs as big and as destructive as possible. Never make a little bomb. Make them so big that you have to recognize that using even one of them means the End of the World.
This was a conscious decision. If a leader thought that he might be able to make a small nuclear strike without ending the world, he might do so and escalation would ensure MAD. So everyone agreed to remove that option. There would be no starting a nuclear engagement thinking that you could back out or stop. There would be no stages, no steps where you could say "that's enough", because realistically, the enemy would never let that happen. As a leader, you had to know that if you launched even a single nuclear weapon, you were ending the world.
So the design philosophy behind building bombs has always been to make them so big that you would never contemplate using them. No litte bombs. Nothing so small where you might think "the Russians might not end the world over such a tiny bomb", because realistically, the Russians would never think such a thing. Only big, giant the-Russians will-retaliate-with-everything-they've-got bombs would do--ones so big that using even one would ensure MAD. Only by raising the stakes so high could we hope to keep the uneasy peace.
Make them so big that you would never contemplate using them. Kerry appears to know his history.
"So what?" you might ask, "The Cold War is over." Indeed it is, but you never know when the next one might start. It's not like Russia still doesn't have more missles than it knows what to do with. But anyway point taken--the Cold War is over and we need to deal with the new reality of Terrorism and asymmetric attacks. So...
Finally back to the original comment in its original context, even in new post-9/11 envoronment he is correct: we must not use, or even contemplate using, "Bunker Buster" nuclear weapons. There is one very simple reason why: the day we use nuclear weapons in a conventional war is the day we legitimize nuclear weapons as conventional weapons. No longer will nuclear weapons be classified strictly as WMD; they will also be classified as conventional weapons. Can we keep other countries from pursuing conventional weapons? Can we even hope to prevent nuclear proliferation when nuclear weapons become a standard part of the conventional arsenal?
Tacitus says that "as commander in chief one d*** well better contemplate using every single nuclear weapon in our arsenal. Most importantly, you NEVER say you won't." While that is generally a sound negotiating policy regarding most weapons, there are exceptions. I see no foolishness in forswearing the use of illegal or immoral weapons, nor in forswearing the use of stupid or non-advantageous tactics. In our current world, the use of Bunker Busters will always fall into one of those four categories.
In both a Cold War environment and in a post-9/11 environment, Kerry's policy is completely sound. Building little nukes that "we might even contemplate using" is just a horribly unwise policy.