first off republicans tried to regulate fannie and freddie(mandated to issue subprime loans under the 95 revision of the cra)in 01,before bush even called for it.the problem stems backs to clinton,under 95 the democrats had pushed for and made happen the revision of the comunity reinvestment act,which made it law for fannie and freddie to issue and buy subprime loans since they were a gse.in 99 sen gramm tried to repeal the glass steagall regs,the repeal was set for filibuster by the democrats,however the democrats caved in under the condition that the repeal would also include loosening regs even further on the housing market and subprime loans to guarantee their support.
in 2000 sen gramm also slips some more deregulation for the financial sector into bill clintons last signed budget,or the first budget used under bush.the problem was expanded by bush trying to expand coverage of the cra even further,even though accounting problems that caused the housing market to crash were evident in 97.bush tried to expand it and also increase regulation.
the problem arose when republicans tried to regulate it,even before bush called for it.each time the bill never made it to a vote because there wasnt a single democrat to support it,meaning it would be filibustered and blocked from vote(kinda the same thing dsemocrats accuse repubs of doing now)so it never made it.the bill failed in 01 and 03,and was re introduced in 05,where it stood stale due to the fact it wouldnt pass a democrat filibuster.john mcain didnt co sponsor the bill until 06,after he had already planned to run for president.
the bill was re introduced in 07,but didnt pass until 08,when it was far too late to stop the bleeding.afterwards in 08 the democrats still defended the cra,most specifically harry reid and barny frank and nacy peloci,who all claimed forcing the big two to buy subprime loans didnt cause them to fail,only a republican mismanagement of the program,yet it was showing signs of failure in 97,a whole decade before.
now the housing problem combined with the repeal of glass steagall,led to a horrible collapse.and yes barrack obama was the lead lawyer pushing for and enforcing the cra's expansion to destructive levels.but then again when bush said it should have strict regulations,he should have stopped pushing it.
when clinton heard of the accounting fraud and the problems in 07,he should have regulated or reversed the 95 expansion,rather than looking the other way at impending recession.