"We have very few good examples to guide us," said William G. Gale, a senior fellow at the Brookings Institution, the liberal-leaning research organization. "I don't know of any convincing evidence that what has been proposed is going to be enough."
Here is the article, from today's NYT. I would reword this slightly, so as to indicate that progrram size alone does not guarantee success. In fact the larger the stimulus becomes, the fewer good examples we have to guide us. Aggregate demand macroeconomics does add a great deal of value to our understanding of the economy, but as in all macroeconomic theories the limits to our knowledge are quite severe.