Sorry, that's 400 BILLION stimulus that Krugman advocated, as a minimum, not 400 trillion.
http://krugman.blogs.nytimes.com/2008/11/10/stimulus-math-wonkish/comment-page-3/
I believe he upped it to 600 billion as unemployment rose, but I don't have the time to confirm that, with a link.

Anyway, Congress refused to pass any direct stimulus.