A week after filing suit against a handful of top lenders, including Ally Financial and its mortgage subsidiary, GMAC Mortgage, Massachusetts Attorney General Martha Coakley has asked the leadership of two key Congressional panels to investigate alleged mortgage-related misconduct by Ally via GMAC Mortgage. In this particular case, Coakley has some unusual leverage: Uncle Sam owns nearly three-quarters of Ally Financial as per a $17 billion investment made in 2008 under the Troubled Asset Relief Program. “In light of Ally’s alleged deceptive and illegal actions against homeowners in Massachusetts and across the country, I respectfully request that your committees investigate Ally’s serious misconduct and consider what actions the federal government can take to ensure that Ally adheres to the law,” Coakley said in a letter to Sen. Tim Johnson, D-SD, chairman of the Senate Banking, Housing and Urban Affairs Committee, and Rep. Spencer Bachus, R-AL, chairman of the House Financial Services Committee.