Dennis is now the anti-Kerry. Plus if you hate Nader there's no better message than to vote Kucinich.
It's a two for one moment in the primary. No way Edwards stops Kerry. The only hope for Dean/Clark/Gephardt supporters to vote in a way that matters is to vote Dennis. Every vote Dennis gets is a message directly to Kerry that positions and issues count.
All other votes are wasted votes from this point on. Why waste it on Kerry he's already got it in the bag. Why waste it on a second place loser. A vote for Dennis at this point carries more weight than any other.