All of which raises the $200 million question: Are these "can defeat Bush" voters correct? Is Kerry the most electable Democrat?
It's a hard question to answer, because most of the evidence is circular. If people support Kerry because they think he's electable, he goes up in the polls, which makes him look more electable. The best way to filter out this distortion is to focus on the voters least likely to make their decisions in November based on electability. These happen to be the same voters who hold the balance of power in most elections: independents, conservative Democrats, and moderate Republicans. They aren't principally trying to figure out which Democratic candidate can beat Bush, because they don't necessarily want the Democratic nominee to beat Bush. They're trying to decide which Democratic candidate, if any, would be a better president than Bush.
How well has Kerry done among these voters? In absolute terms, well enough. But in relative terms, the numbers show a disconcerting pattern. By and large, the closer you move to the center and center-right of the electorate, where the presidential race will probably be decided, the worse Kerry does.
It always galls me that the 'moderate' wing of the dems is 'conservative' but the 'moderate' wing of the Reps is not 'liberal'. It reveals the media bias so clearly. When have you ever heard of a liberal R (except for Toomey's primary rebellion against truly liberal Spector)? And when people talk about a 'moderate' dem, they mean the center of the D party, not the center of the whole spectrum.