Forget Rick Wagoner and the UAW. There's a potentially bigger winner in any bailout of Detroit: Wall Street.

The list of banks involved in loan deals with General Motors (GM) and Ford Motor (F) is a who's who of the finance industry. Ford's debt includes an $18.5 billion credit agreement with J.P. Morgan Chase (JPM), Citibank (C), Goldman Sachs (GS), Deutsche Bank (DB), HSBC (HBC), Morgan Stanley (MS), Lehman Brothers and others. GM has a $4.5 billion credit agreement with a group of banks including Citi and J.P. Morgan.

It's difficult to know exactly which banks currently hold how much of the auto makers' debt. Despite their pleas for the public to care about their plight, both GM and Ford are tight-lipped on the matter. Ford says it doesn't disclose its banks and works with many lenders. A GM spokeswoman told us the company is too busy to answer queries that aren't clearly to its "benefit."

But it's reasonable to assume that at least some of the Wall Streeters on these credit agreements still have exposure to the auto makers. And sob stories aside, the ultimate reason we're rescuing Detroit is so it can avoid defaulting on its debt obligations. GM has said that without government help, it "will default in the near term," while Ford has said that a collapse of one of its U.S. competitors would threaten its own ability to stay alive.

Perhaps it's this prospect of yet another bank bailout, even a stealth one via an auto rescue, that has financial stocks picking up recently. The Financial Select Sector SPDR (XLF), which tracks financial companies in the S&P 500, has gained some 30% since the beginning of December, when it started to look more likely that Washington would throw Detroit a lifesaver.

If GM was forced to file for bankruptcy in lieu of a bailout, and Ford followed suit, their banks would be in for a long and messy fight even though their loans are technically secured. After all, they don't call it bankruptcy "protection" for nothing. Bankruptcy shields companies temporarily from creditors so management can reorganize finances and operations, and hopefully emerge stronger. This means even secured bank lenders aren't guaranteed to get 100% of what they re owed. They're just first in line for repayment.

"Like everyone else [secured banks] run the risk there will be an erosion of the residual value of the company," says Jack Williams, resident scholar at the American Bankruptcy Institute and a bankruptcy law professor at Georgia State University. For instance, if GM owes a bank $100 but the collateral for that debt is now worth only $70, a bankruptcy judge could allow GM to pay only the $70 and force the bank to take a $30 loss. That could be a devastating blow to a banking industry already drowning in bad mortgages.

"There's actually a lot of flexibility in handling secured claims in a Chapter 11 reorganization," Williams says.

Standard & Poor's estimates that GM's secured lenders would recover 90% to 100% of what they're owed in a bankruptcy, which is about $6 billion, says associate director and auto analyst Gregg Lemos Stein. Ford's lenders, however, would get closer to 50% to 70%, because it has much more secured debt outstanding. The more debt, the harder it is to pay it all off. These estimates assume the bankruptcies would lead to reorganizations, not liquidations, of the companies.

But Morningstar analyst David Whiston says that "without any [government] help GM would go into Chapter 7," which is a liquidating bankruptcy. If this happened, good luck to the banks. "In liquidation creditors can start selling off plants and hope Toyota (TM) or Nissan wants to buy them, but in this economy they're not likely looking to spend lots of money on acquisitions," Whiston says. "So it'd be at fire-sale prices, and that's what creditors would get: pennies on the dollar."

Banks are already on life support because of their risky home loans, so taking losses on auto debt is the last thing they want. "This is a very difficult time for banks, so I have to believe they will be considered in any type of [auto bailout] package," says Damyon Mouzon, president of credit ratings firm Lace Financial. Luckily for Wall Street, and thanks to taxpayers, it s shaping up to be Uncle Sam to the rescue one more time.