The latest Washington Post/ABC poll finds that Hillary has a 62-15-14 lead over Obama and Edwards among Democratic voters on the question of who has the best chance of being elected president. That's up from 57-16-20 in late September and 43-21-26 in June. It's worth pointing out, as the rival campaigns will tell you, that electability numbers often closely reflect a candidate's overall standing in the polls. But I think the two numbers interact in a somewhat less obvious way, too: If you're leading by a comfortable margin, there's less pressure on you to take positions that will excite your party's base, which preserves your centrist bona fides for the general election, and therefore helps make you more electable. If, on the other hand, you're trailing in the polls, you've got to take more risks, which often entail hugging your party's base, which makes it harder to compete in a general election. So it's not just that electability numbers coincide with overall poll-standing because voters use the latter as a proxy for the former (though I'm sure that's a big part of it). There is some way in which the latter actually causes the former.