The notion that the economic crisis was caused by Barney Frank and Fannie and Freddie Mac has gained extremely broad currency on the right, but is so silly economists pay no attention to it at all. Paul Krugman has a great blog post summing up the ridiculousness of the whole notion:
1. The Community Reinvestment Act of 1977 was irrelevant to the subprime boom, which was overwhelmingly driven by loan originators not subject to the Act.
2. The housing bubble reached its point of maximum inflation in the middle years of the naughties:
Robert Shiller
3. During those same years, Fannie and Freddie were sidelined by Congressional pressure, and saw a sharp drop in their share of securitization:
FCIC
while securitization by private players surged: