Donaldson was too tough on Wall Street, so he got the ax.  Then you had Christopher Cox, because he wasn't going to do his job.  That's why he got the job.

The five commissioners of the S.E.C. are securities lawyers.  Securities lawyers never understand finance.  They don't have the math background.  If you can't do math and if you can't take apart the investment products of the 21st cntury backward and forward and put them together in your sleep, you'll never find the frauds on Wall Street.

Harry Markopolos in Deborah Solomon, "Math Is Hard", The New York Times Magazine, Feb. 28, 2010.