I think it's useful to just go back in time and see what one side was saying and what the other side was saying prior to the economic downturn. Who understands things and who doesn't? I've talked about Mark Perry from the right wing American Enterprise Institute. Take a look at what Krugman had to say in 2006. Who knows their stuff and who doesn't?
Krugman has been criticized because in 2002 he recommended policies that would create a housing bubble in order to get us out of that recession. Basically it was some Keynsian stimulus for a slumping economy. It worked temporarily and blew up in our faces in 2008. But sometimes people don't know that in 2005 Krugman saw that as well. He said sure, the bubble was necessary. It was implemented and it worked. But at this point it's gone on too long and must be scaled back. So he seems to have understood what was going on.