Text quoted from Powerline is self explanatory, both pages of letter plus signatures available by clicking either link in the center.
Bold emphasis mine for speed scanners.
....."One thing I hadn't realized is that McCain's reform legislation was passed through the Senate Banking Committee, but was not able to gain majority support on the Senate floor. All twenty Senators who signed the letter calling attention to the urgency of reforming Fannie Mae and Freddy Mac were Republicans. After May 2006, the Democrats continued to use Fannie and Freddy as their private slush funds until the inevitable collapse, which McCain had warned against so eloquently, occurred.
For some inexplicable reason, John McCain seems unable to claim the credit he deserves for being one of the few politicians in Washington who saw the present crisis coming and tried to do something about it. He is even more unable to vigorously and unambiguously put the blame where it belongs: on the Democratic Party. Which is one of the principal reasons why, as everyone expects, he will lose in November."