Broadly speaking, the serious contenders for the Democratic nomination are offering similar policy proposals  the dispute over health care mandates notwithstanding. But there are large differences among the candidates in their beliefs about what it will take to turn a progressive agenda into reality.

At one extreme, Barack Obama insists that the problem with America is that our politics are so “bitter and partisan,” and insists that he can get things done by ushering in a “different kind of politics.”

At the opposite extreme, John Edwards blames the power of the wealthy and corporate interests for our problems, and says, in effect, that America needs another F.D.R.  a polarizing figure, the object of much hatred from the right, who nonetheless succeeded in making big changes.

Over the last few days Mr. Obama and Mr. Edwards have been conducting a long-range argument over health care that gets right to this issue. And I have to say that Mr. Obama comes off looking, well, naïve.