I don't see the Carter analogy, because I doubt Bush will be thought of as "failed" by his own side. I vividly recall wearing a Kennedy '80 button outside a polling booth in Massachusetts at the time of the Mass. primary. I eventually cast my ballot in the fall for Barry Commoner of the Citizens Party

I am supporting Clark, and I don't think it's at all too late. The mushrooming energy from the grassroots I'm seeing reminds me a lot of Perot '92 1.0 (I worked for Perot until he dropped out, and did not support him after he dropped back in)

The analogy favored by Clark supporters is 1952, in which a country mired in war turns to a centrist general of the opposite party. I've blogged it here:

http://centristcoalition.com/blog/clark/archives/000093.html