I also wonder if it was a good idea to announce so early. This is one of, if not the, earliest announcements of a VP choice in modern times. It usally comes much closer to the convention.
I wouldn't say three weeks before the convention is all that early. It just seems early because of the early Dem convention. Unless the campaign finance rules change between now and 2008, I don't expect we'll see either party hold their convention in July next time.
As I was adjusting my prediction to take account of the pick of Edwards, I realized that Edwards gives Kerry an extra boost in Florida because of how he affects the age demographic of voters, making the average likely voter younger. Bush has been pushing the embargo on Cuba to woo the
Cuban-American vote, but the younger ones see themselves more as Cuban-
American and aren't as virulently anti-Castro, perhaps because they know they will outlive Fidel. It took adding in that effect in addition to the generic Edwards bounce for me to change my prediction for Florida from a Bush tossup to a Kerry tossup.