My observation is that re-electing Kerry is solely "anyone but Bush - or a Republican". It has zero to do with the merits of Kerry as a President.
Virtually every person I've ever discussed the election with, that was pro-Kerry, discusses how bad Bush is, and almost to the last person, admits they don't know what Kerry's position on anything is.
The die-hard Bush haters WILL vote on what they think, but the more inertial moderates aren't likely to drive to the polls to unseat someone they have few opinions on.