Picking a VP candidate early creates the potential for stagnation after the convention. But then again it seems kerry needs a boost at the moment because there isn't much energy surrounding him. It seems as though kerry has decided he needs the boost choosing a VP candidate can bring now instead of later. Desperation? Not necessarily, but it may be a signal that the heat of the spotlight is wearing on him and he needs a big diversion.
There has been MAJOR posturing done by a few to try to catch kerry's eye, but I think one of the most flagrant examples is Iowa Governor - tom vilsack. It was quite the political move to have your wife endorse kerry when the other "big" dems in Iowa were supporting the scream machine dean. Vilsack couldn't risk endorsing dean because he'd look like a fool when he lost the nomination - just like Harkin looks like now.

Anyway, it was quite a ingenious move on his part - stick his wife out there for the "establishment" candidate and still stay quiet yourself so as to not buck Harkin or other leftists here.
There are other things vilsack has done to audition for the VP spot, but those can be addressed when he gets picked.
tom pillage-N-sack is who I'm putting my money on for kerry's VP pick. Not only will vilsack not overshadow kerry on charisma like other VP picks easily could do, he would also help shore up the mainstream dem vote for kerry(since kerry hasn't exactly lit them on fire).
I'm sure Bowfinger has an opinion on the viability of pillage-N-sack as kerry's VP since Bow lives here in Iowa too and has witnessed the political show he's been putting on.
CkG