There is an excellent piece in the Examiner by Michael Barone (building on a blogpost by Megan McArdle) on why Obama cannot govern today as FDR did in 1933. He examines the factors that made 1933 a unique political opportunity, one that cannot be replicated ever again, and in the course of doing so exposes important dimensions of change that have taken place in this country in the intervening decades.
It's an interesting and informative read. Check it out here.