Apropos of my post yesterday on electability, Mark Blumenthal of Pollster.com had an interesting post about this a few weeks back. His conclusion: Electability is mostly a function of a candidate's experience (or at least perceptions of it) and how they're faring in campaign coverage (which is often a function of national polls).
For what it's worth, I largely agree with Mark. My point was just that the way a candidate is faring in polls and campaign coverage often influences their strategy, which can then, at the margins, affect perceptions of electability. Take Bill Richardson. I suspect there's some subgroup of Iowa voter who liked his pledge to get us out of Iraq immediately, but nonetheless wrote him off when he made it for fear that he couldn't win the general election. Now I doubt Richardson would have moved so far left on the war had he been doing better in the polls. So Richardson's "unelectability" was in some sense driven by his low poll-standing rather than simply reflecting it.