I want to note one sentence in the piece by Stephen F. Hayes that I just linked. It's from Bruce Riedel, who led Obama's own review of the Afghanistan situation:

That's a part of the process that's a legitimate question for a president--if I do this, can I sustain it with political support at home?

He's right, it's a legitimate question, and it helps explain why Bush didn't push harder to reform Fannie Mae and Freddie Mac (and why the effort he did make is significant). The Democrats were solidly against him and the Republicans were flimsy at best. Now that Obama's in office with a strong electoral victory and his own party the majority in both houses of Congress, yet he's finding he needs to tread cautiously—should we wonder that Bush couldn't accomplish more of his agenda?

(This video of a 2004 Congressional hearing on Fannie and Freddie makes for astounding viewing in these post-collapse days.)