My take is that this represents an uprising from the older branches of the Democratic Party that have gotten tired of it being run by the Clintons and their allies (which it has been, even through the last 8 years). I think Ted sees Obama as someone who will be willing to take directions from his branch.

A lot of this kind of thing has been going on in the Republican Party, too. Right now, it's a struggle between the principled conservatives and the pragmatic "reasonable" ones. The Rockefeller Republicans, who used to be on one end of this tension, are pretty much out of the picture now.