Would a government bailout of Fannie Mae and Freddie Mac put even more downward pressure on the U.S. Dollar?

“Here’s a scary, and relevant, question to ponder as the housing market continues to slide: What would it take for the government to step in and help Fannie Mae and Freddie Mac, and how would a rescue affect you, the taxpayer?

It’s been a brutal week for Freddie (FRE, Fortune 500) and Fannie (FNM, Fortune 500). A Lehman analyst report Monday kicked off a stock rout that had shares in both mortgage lenders hitting fresh multi-year lows Thursday. Freddie was down 19% in afternoon trading; Fannie was down more than 10%.

The stock plunge, together with Fed Chairman Ben Bernanke’s downbeat housing outlook on Tuesday, is forcing investors to consider what would happen if a bailout is needed – a prospect raised Thursday when William Poole, the former president of the St. Louis Federal Reserve, told Bloomberg the companies are already ‘insolvent.’”

“Clearly, investors are concerned. Credit default swaps – a kind of insurance against the possibility of Fannie and Freddie defaulting on their corporate bonds, are at their most expensive levels in 14 weeks; both companies are expected to report steep losses for the second quarter; and their main business, mortgage securitization, is under pressure as home price values decline and foreclosure numbers rise.

‘The major issue is that these are very leveraged financial institutions, leveraged much more than any other bank, and they have lots of mortgage assets. As real estate values decline every day, the value of [the mortgages that it bundles, guarantees, and sells] are called into question,’ says Dalton Investments co-founder Steve Persky, who has been focused on distressed mortgage assets.”

“The Federal Reserve and the Treasury have taken great pains to point out that the government is not obligated to bail out either Fannie or Freddie if they face insolvency.

It’s debatable where the legal obligations lie, but as a practical matter, the government can’t let these institutions fail because they are being counted up on to help fix the mortgage mess. If Fannie and Freddie were unable to buy and back loans, banks would stop originating them and the pool of homebuyers would shrink, causing home prices to fall even further.”

“In an April report, Standard & Poor’s said an Armageddon scenario whereby Fannie and Freddie are insolvent is unlikely, but that the mere possibility of failure at either is a greater threat to the economy than the actual collapse of any investment bank.”

“The doomsday scenario could cost taxpayers more than $1 trillion, says the S&P report. The report went so far as to say that a government bailout of Fannie or Freddie could force the agency to lower its rating on the creditworthiness of the United States.”