While I'd say there's a surprising degree of broad ideological agreement among people who read and comment on major lefty blogs, I think that serves to mask a great deal of disagreement about priorities. I'm not suggesting that there's lockstep agreement on all policy issues, but it seems the greater differences are about priorities.
Especially in debates about the presidential hopefuls I see people seeming to talk past each other because they aren't really disagreeing about the issues, they're disagreeing about how they prioritize those issues.
