Ezra Klein (with Dylan Matthews) had a great primer on the debt limit, both in general and the current fight, earlier today that I highly recommend. Klein also had a very nice item about the debt and the ratings agencies just now that I'd like to recommend, except for one thing. It's called "How Congress put our credit rating at risk."
In my view, and I believe in Klein's view, this is wrong. The piece would be accurate if he replaces "Congress" with "Republicans" each time. Or, if that's not what he believes, then he should be talking about "Congress and the president" throughout. But I don't think he believes that. I don't think he believes that Nancy Pelosi, or Harry Reid, or Kent Conrad, or Steny Hoyer has put our credit rating at risk. And I don't think he believes that Barack Obama has.
(For what it's worth, I don't believe that Mitch McConnell or John Boehner or Tom Coburn has, either, although in each of these cases, including with the Democrats, I'm open to evidence to the contrary).
No, I think it's Republicans, both in and out of Congress, who are threatening the economy. And they deserve to be called on it.