I think Dick Morris offers an interesting thought.

“The demise of Howard Dean’s candidacy opens the door to a Kerry/Clinton
ticket in 2004. As long as Dean was favored to get the nomination, Hillary
likely wasn’t interested in the second slot on the ticket. With the Vermont
governor almost certain to go down to a massive defeat, Hillary probably
wanted no part in the ensuing carnage. But now that the Democrats have a
real chance to win, it makes all kinds of sense to offer her the nomination
and for her to accept it.

“…Very few vice presidential candidates can actually win votes for the top
of the ticket: Hillary can. She is the most popular Democrat in the nation.
And a woman vice presidential candidate – particularly Hillary – would
electrify the Democratic base and guarantee a huge turnout. It would
transform a campaign into a crusade. The voters she’d alienate? Already
voting for Bush.”

– Columnist Dick Morris, New York Post.

And Summer, the Will column is worth the read!