I happen to believe that much of what we're hearing about the VP selection process over the last few days has been carefully designed to mislead, so take this "clue" with a grain of salt.
According to CNN's Morning Grind today, "The site and date of Kerry's announcement are locked in. Where will Kerry clasp hands and raise arms with his guy? We received this tea leaf from a Kerry advance aide: 'I wish I was going to Pittsburgh.'"
http://www.cnn.com/2004/ALLPOLITICS/07/05/mon/index.html
Of course, it could be yet another head fake from the Kerry team, but why would the announcement be in Pittsburgh of all places? Unless ... Pittsburgh native Tom Vilsack is the choice.