Financial reformers seeking new rules beyond the range of the Dodd-Frank law haven’t had much to cheer about this year. The chances of Congress passing new regulations—OK, passing anything—look bleak, and the Obama Administration wants to simply finish implementing the last set of reforms. But reformers are playing a longer game, biding their time until the conditions are ripe for a dam burst. That could happen sooner than you think. High-profile champions for reform are gradually bending regulators to their will, and a pile-up of big bank abuses have eroded Wall Street’s reputation in Washington. Most importantly, a new report detailing the extraordinary largesse granted banks during the financial crisis, and questioning whether Dodd-Frank would prevent a rerun, could set off a fresh spark.

An unlikely bipartisan duo, Senators Sherrod Brown and David Vitter, have tried all year to focus attention in Congress on ending “too big to fail,” the perception that large financial institutions will inevitably receive government bailouts if they run into trouble. This allows banks to take on outsized risks with implicit government support, and receive a de facto subsidy, with lower borrowing costs than their smaller competitors, because investors believe a backstopped institution will always pay them back. Brown and Vitter introduced legislation earlier this year to significantly raise capital requirements, which they say will reduce reliance on bailouts by forcing banks to pay for their own losses.

Brown and Vitter commissioned a study from the Government Accountability Office (GAO) to quantify the public subsidy bestowed on banks, which could give them powerful evidence to rally support for their legislation. GAO released the first part of the study last week. It mostly looks backward at the “extraordinary support” given to banks from 2007-2009 to weather the financial crisis, and whether the Dodd-Frank financial reform law ended this tendency toward bailouts. The more controversial part of the study, on how much the government subsidizes big banks considered too big to fail, isn’t due until next year.

But the report still contains some explosive material. It details how banks received trillions of dollars in capital injections, emergency lending and debt guarantees during the financial crisis, offered with more favorable terms than they could have found in the private market, and secured by junk collateral that non-government lenders would never accept. Some debt guarantees given by government agencies to banks were up to 10 percent cheaper than private alternatives, saving the banks billions of dollars. Banks with over $50 billion in assets used the crisis-era programs nearly twice as much as their smaller counterparts. Outside of the broadly available emergency programs, JPMorgan Chase received a $30 billion loan from the New York Federal Reserve (then run by Timothy Geithner) for its purchase of Bear Stearns, and both Citigroup and Bank of America received special direct assistance of $20 billion each. According to a summary released by Brown and Vitter, those three banks, the U.S.’s largest, would have been insolvent without the government support provided during the crisis. Since the biggest banks are even bigger today (the report states that the nation’s four largest banks are $2 trillion larger than they were in 2007), it’s hard to believe that similar support wouldn’t be granted if needed.

Dodd-Frank’s architects claim the law would prevent future bailouts. At least some of the market is convinced it would; the rating agency Moody’s downgraded the debt of major U.S. banks last week, after determining they would not have the advantage of future government support in a crisis (it’s worth noting that rating agencies receive the majority of their funding through the structured finance deals of these same big banks). But the GAO report concludes that Dodd-Frank “implementation is incomplete and the effectiveness of some provisions remains uncertain.”