Republicans used the debt ceiling to extract cuts from the Democrats, but they didn't make sure they got only the cuts they could stomach. Somehow, the wily Dems managed to get the Republicans to agree to a little pain themselves. Only now the Repubs are talking about reneging on the cuts they don't like, namely the defense cuts.
How did this happen? Because the Republicans no longer know what compromise feels like. They want what they want, and they don't want to give up anything else. Sounds like a spoiled child. That child is maybe going to get a lesson, but I wish it was sooner than 2013, when the cuts are finally due to bite. Can the Republicans take the medicine that they urge on so many others, and that they agreed to? I don't know. At this point, I'm expecting kicking and screaming, not adult behavior.
Update 11/22/11. For analysis of the bargaining positions, see this post.