I don't put a lot of stock in electability arguments. That said, Tom Edsall highlights some interesting data from the polling that's been done on Clinton-McCain and Obama-McCain:

The Cook Political Report/RT Strategies poll of 855 registered voters conducted January 31 to February 2 found that Obama ran significantly better than Clinton among independent and Republican voters in a contest with McCain, while in a Clinton-McCain matchup, Hillary did better than Obama among Democratic voters. The same pattern emerged in a FOX News survey of 900 registered voters on January 30 and 31.

[snip]

On the surface, the differences between Clinton and Obama -- ranging from 4 to 12 percentage points -- may not appear significant, but in practice elections are won and lost at these and even much smaller margins. Obama runs 4 points behind Clinton among Democrats, 75 to 71, in match-ups with McCain, but he runs 4 points (14-10) and 12 points (50-38) better than Clinton among Republicans and independents. [Emphasis added.]

I think there are plenty of good reasons to doubt that some of those Republicans currently singing Obama's praises won't be so fulsome in their praise for him if he's the actual Democratic nominee. (I'm looking at you David Brooks!) But is there any reason to think that Clinton's lead over Obama among Democrats wouldn't basically evaporate if he's the nominee? I thought it was the Obama supporters who were supposed to hold the bigger grudge.

--Jason Zengerle