I realized the other morning that I've voted, at one time or another (and, in one instance, twice) for each of the three leading people running for President. I wrote in John McCain in 2000, since I couldn't stomach voting for Bush and wasn't nearly as enthusiastic about Al Gore as I would be today. I've voted for Clinton twice in her Senate races. And I voted for Obama in the New York primary this year. You'd think I'd be happy, therefore, with whoever wins. Not exactly.
I suspect that the worst tactic either Barack Obama or Hillary Clinton could engage in right now is to attack each other as a way to get the nomination. Not just because it's potentially damaging to the Democratic party. But I wouldn't be a bit surprised if every vote their campaigns gain from "making distinctions" for voters (i.e., going negative) loses them another vote elsewhere. Plus a vote for John McCain in the general election. So go negative, but you risk losing the nomination and will in all likelihood lose the general election even if you get the nomination.
Wouldn't it be far better (and more effective) if both of these candidates took on John McCain now? Wouldn't the candidate who can, today, make the best case against John McCain -- and make it consistently -- earn the right to make it in November? For that matter, since they're both in the news until one wins the nomination, wouldn't it be far more effective to have two voices making the case against McCain than to wait until after the convention to start doing that?