????The struggling auto and mortgage lender may get a third bailout -- which means that the government could end up owning more than half of GMAC.

????By Colin Barr, senior writer

????NEW YORK (Fortune) Will the third bailout be the charm for GMAC?

????The troubled auto and mortgage lender is looking for a third round of federal assistance.

????As part of this spring's stress tests of the nation's largest banks, the government told GMAC to raise at least $5.6 billion from private investors by Nov. 9. GMAC confirmed Wednesday that it is working with regulators to strengthen its finances.

????"GMAC is working with the Federal Reserve regarding the remaining capital requirements related to the stress test results," spokeswoman Gina Proia said. "We fully intend to comply with the requirement for additional capital related to the stress test."

????If regulators were to inject enough capital to fill the stress test hole, taxpayers could end up owning more than half of the company. The Treasury Department already owns more than a third of GMAC, thanks to $13.5 billion in capital injections in December and May.

????GMAC's difficulty in raising new funds from investors highlights the problems troubled lenders everywhere are having raising capital.

????Some of the biggest banks, led by Bank of America (BAC, Fortune 500) and Wells Fargo (WFC, Fortune 500), succeeded in raising tens of billions of dollars after the government's stress tests in May.

????But more than 100 banks have failed so far this year, including big regional banks such as Colonial BancGroup of Alabama, and many more are expected to fail as the industry struggles to absorb a wave of defaults on commercial loans.

????With loan demand weak and past loans going bad at a rapid rate, being told to raise new money amounts to a death sentence for most institutions, regardless of their size.

????"Try raising tens of millions of dollars in this environment," said Linda Keith, an Olympia, Wash., banking consultant whose firm trains community bank employees. "The government can dump all the money it wants into the economy, but the banks are still getting squeezed."

????But the Obama administration has indicated it will back GMAC because it wants to support the struggling domestic auto industry.

????General Motors, the biggest U.S. carmaker, emerged from bankruptcy earlier this year and No. 3 vehicle seller Chrysler was sold to Italy's Fiat.

????The government stressed that the problems at GMAC aren't new. "GMAC is the only one of the banks that went through the stress test to need additional government capital," Treasury spokesman Andrew Williams said Wednesday.

????GMAC has lost $4.6 billion so far this year and has posted losses in seven of the past eight quarters, as vehicle lending has plunged along with demand for cars and its subprime mortgage loans have gone bad. It is scheduled to post third-quarter numbers next week.

????New aid to GMAC would come as officials are emphasizing how many banks have been able to repay Troubled Asset Relief Program loans.

????"It will depend on the institution, but for major banks in the country I think that money will come back relatively quickly," Treasury Secretary Tim Geithner said at a securities industry conference Tuesday.

????GMAC is also getting clearance from the Federal Department Insurance Corp. to issue an additional $2.9 billion of federally guaranteed debt -- just days before debt issuance under that plan is scheduled to end.

????Earlier this year, the FDIC told GMAC it wanted to sign off on any subsidized debt-issuance plan before GMAC went to market, in a nod to the firm's financial problems and the aggressive deposit gathering at its Ally Bank unit.

????"We are focused on transforming the company, restoring financial health, and maximizing the investment by our shareholders," Proia said.

????CNNMoney.com's Jennifer Liberto contributed to this report.