From a recent post on the speculation regarding a post-Iowa "bump" for Obama:
"One more thing. I cannot point to an academic study to prove this, but most campaign pollsters will tell you that when a candidate is gaining, vote preference is usually the last thing to change. The movement usually shows up first on internal measures. So on that score, consider that the UNH survey, which shows the smallest "bump" also shows a huge shift on perceptions of electability. Ten days ago, likely Democratic primary voters in New Hampshire considered Clinton the "candidate with the best chance of defeating the Republican" by a a two-to-one margin (45% to 22%). Obama has closed that margin on the most recent survey to a single percentage point (Clinton 36%, Obama 35%)."