David Swanson has some reasons for supporting Kucinich:

Most Americans won't start paying attention to this election until AFTER the Democratic nominee is chosen. If we choose one who presents a contrast to the President, we will excite people and turn out new voters, in addition to all the regular voters who plan to vote for whoever the nominee is. And we all can support whoever the nominee is. But now is our opportunity to make that nominee a candidate who can revitalize our democracy and defeat President Bush by calling for fundamental change, not staying the course but altering the rhetoric. That Dennis Kucinich will make the strongest candidate against Bush is hard to dispute. That he is not ahead of other Democrats in the polls is no reason not to vote for him in the primary. A primary is a chance to vote for the best candidate. If he doesn't win, you've helped promote his platform at the convention. If everyone who says "Dennis is my first choice but he's not electable" turns off their televisions and talks to their neighbors and votes for him, he will be elected, "electable" or not.

(from a recent newsletter)