From my mortgage broker on September 8 2008:

“Mortgage rates are dropping significantly due to yesterday’s announcement that Fannie Mae and Freddie Mac will come under control of the government. This announcement came as the government felt both these institutions will no longer be able to meet their mission statement, which is to provide liquidity, stability and affordability in the housing markets.

In summary, the problems in the mortgage industry of late have made it difficult for Fannie and Freddie to issue new Bonds, and thus meet the capital requirements to pay off maturing Bonds. The Treasury stepped in to guarantee the payments on these new Bonds, which will make Mortgage Backed Securities more attractive to investors; these Bonds will have higher yields than Treasuries, with the same government-backed guarantee.

This action by the government will have two major effects. First, rates will drop significantly, possibly around 100 bps (from 6.250% to 5.250%), which will make mortgages more affordable for more borrowers. Secondly, this action will make credit easier to obtain, allowing for more borrowers to obtain home loans. Both effects will help slow, and possibly stop, the housing value downturn the country has experienced these last 18 months.”