Where Does the Pain Caucus Come From?

Paul Krugman meditates on the Pain Caucus:

http://krugman.blogs.nytimes.com/2010/06/02/interests-and-ideas/: Lambert has a righteous rant about my Monday column.... Fair enough.... Now, none of those people [leading the Pain Caucus:] are... likely to find themselves... among the long-term unemployed. So class is certainly a factor. But I find myself in conversations with people I don't think have a deep urge to inflict pain and/or safeguard the rentier class who nonetheless ask, "But...