Dean is optimistic
(Updated for maximum linkage)
So the Bush campaign is allegedly going to push the idea that Dean is a pessimist (and Bush is an optimist) on the theory that people will vote for the optimistic candidate over the pessimistic candidate every time (good comments on this strategy can be had from Matthew, Atrios and Kos).
To some extent this is true. People prefer the positive outlook. (think Carter's malaise vs. Reagan's morning in America). But there is more to being optimistic than just having a sunny disposition. Optimism, for me, means believing that, no matter what happens, you can overcome it and still achieve great things.
Since Dean is a doctor, he should approach it in the same way he would approach a cancer victim: be realistic in his assessment of their condition, but be optimistic that they can defeat the cancer that is eating them up from the inside. But first they have to avoid the quack selling snake oil. The quack who is trying to fool them into thinking he can take away all their problems. The quack isn't optimistic. He is opportunistic.