Doesn't matter what their position was, they weren't in charge of the Congress during those critical years when lenders were going crazy writing toxic loans. Republicans were in charge and they didn't pass any oversight or regulations which could have prevented the meltdown.
I know someone who was offered $30,000 by a bank to buy a house, unseen. The bank offered to sell him a house he would never see, they would pay the closing costs, they would pay the first six monthly mortgage payments, they would pay the real-estate taxes, and to collect $30,000, he would have to wreck his credit and give the house up to foreclosure after 6 months. That was back around 2004-2005, before the system was inundated with foreclosures. That's the kind of **** that was going on.
In Congress, Democrats were on the complete wrong side of the issue, no doubt -- but until 2007, they weren't in charge. By then, the damage was done. Republicans were in charge and they dropped the ball. They are mostly responsible no matter how much you try to push that responsibility onto Dodd and Frank, two members of the minority party.