The problem is the fear that Hillary will win the nomination by destroying another Democrat and that way of winning would be seen as illegitimate. It's one thing to run a hard campaign and make the other candidate show his or her mettle. It's another to destroy them by helping the Republican candidate who will run against them in the fall.

Right, that's exactly the problem here. The "Hillary wins, Obama loses" and "Obama wins, Hillary loses" scenarios aren't symmetric. This entire discussion is predicated on the idea that the only way Hillary can win is by going extremely negative on Obama. Right now, Obama's more electable by a hair (head to head polls against McCain). And if they continue the worst-case-for-Obama pattern of 50/50 delegate splits like March 4th, he wins handily.

In other words, if Obama wins, he'll have done so through the same largely clean, positive campaigning he's used thus far. He'll hopefully resist the pressure to go negative, and stick to "fair game" attacks and defensive measures. This will alienate a minimal amount of Hillary's base (basically, the hard-core who believe that Obama was using sexist attacks from day one) and nominating a qualified woman could be an excellent way of patching up Obama's relations with the remainder. The Obama campaign would, of course, have access to the polling and demographic data that would let them actually make this decision.

If Clinton wins, she'll presumably have to do so by going all-out on Obama, and unloading smears, lies, and deceit. This will alienate large chunks of Obama's base, since Democrats are supposed to be above that kind of Rovian slime. We're not just talking the hardcore, we're talking all the people he drew in with talk of change and a new type of politics.

Now, if Clinton can manage to win without going hard-core negative and demonstrate an adoption of the same new type politics, it's possible that she wouldn't alienate Obama's base. But I think that's highly unlikely. Her only win condition seems to be lies (like the NAFTA smear), racism, and fear.