Chait shoots an arrow through its heart:
Roosevelt generally enjoyed broad public support despite having no success at persuading Americans to share his Keynesian view. (Westen subsequently writes, "if you give [Americans] the choice between cutting the deficit and putting Americans back to work," they'll favor the latter. But the problem is that Americans don't see that as a choice, which is wrong, but not a form of wrongness any president has succeeding in correcting.)
Roosevelt's fortunes are a testament to the degree to which political conditions are shaped by the state of the economy. Roosevelt was wildly popular during the recovery, which coincided with his populist 1936 reelection campaign. Yet Roosevelt's most populist governing period came after that election, when he took on the Dixiecrats. That period coincided with an economic relapse (caused by his premature abandonment of fiscal stimulus) which in turn severely damaged Roosevelt's popularity. All these facts are rather hard to square with Westen's narrative — not a surprise, I suppose, given his professed favoring of simple narrative over complex facts.
A Monkey Cage commenter points to a TNR editorial from 1933 that reads:
The head of a coalition government, accordingly, can exercise his freedom of action only within limits; the moment he irrevocably alienates his support on either the Right or Left, he is through. In the case of Mr. Roosevelt, you find that while he has acted with amazing boldness and imagination on a multitude of questions, he has shown great reluctance in facing up to a fight on any single clear-cut issue.
The Dish 