Newsweek Poll's 19 Point Shocker: Updated

PHILADELPHIA -- Newsweek's national poll of Democrats is certainly attention grabbing. The survey was conducted April 16 and 17 and shows Barack Obama with a 19 point lead (54 to 35) over Hillary Clinton. That certainly draws a contrast with Gallup's daily track, which is, I believe, a three night rolling average. Why is Clinton dropping below her standard 40% floor? Newsweek attributes it to a steady decline in the number of Democrats who find Clinton honest and trustworthy. In any event, for those looking for evidence of the theory that Clinton gets hurt everytime Obama is attacked (even when it's not by her), here it is. I suppose that Clinton supporters will take comfort in Gallup's numbers. There is reason to be skeptical at this point about the importance of these national surveys; I'd love to know, for example, how many Hillary voters have switched to Obama. That's something a panel survey (something that AP, Gallup and CBS News/New York Times all do at certain junctures) could tell us. I wonder also about retrospective bias. That is, most of the folks sampled have already made a choice; to pollsters, they're asked to re-evaluate that choice through the lens of the present. And the lens of the present, of course, is a lens that focuses on Barack Obama as the nominee.

Updated: (Reader K: "The Newsweek poll says that they sampled registered Democrats and those that "lean Democratic", which I assume means independents who traditionally vote Democratic. I think the Gallup poll is registered Democrats only, which would explain the discrepancy.")