Re: bumps. The polling is in hyperdrive to test any movement due to Biden. Of course, I suppose an additonal day's wait would be prudent... Sometimes, the general polled public is a bit slow to attach events to their answers...but I'm imagining the question would be forthright: Does the Biden selection change your vote? Seems like that would show up sooner than hazier questions or events...
Hazier... like the Iowa win?
Same idea. "Does the Iowa win change your vote?"
It just takes a while to percolate. Some people don't get the news itself right away. Some people are dependent on spinmeisters to clarify what they think. Some people learn more about implications of it ("Iowa means that Obama can win the white vote which is significant," "Iowa indicates that the Obama campaign is better organized than Hillary's) (or, "Biden is an especially good debater," "Biden is from Pennsylvania and still has strong working-class ties there") and that's
what influences their decision.
Again, we're political junkies -- a whole lot of people out there, when initially asked their opinion of Biden as VP, are likely to say "who?" They're going to learn a lot more about him as the coverage of him percolates and as the Dem conventions get started.
The bump-delay was a surprise to me, too, when I first learned about it, but since then I've seen it over and over again. Robert referred to this, too. ("No European trip bump! Hah!" <a bit later> "Oh, there it is. Oops.")