The Congressional Budget Office confirmed on Monday that bank lobbyists had successfully altered language of the so-called Citigroup carve-out, potentially allowing mega-banks Citi and JPMorgan Chase to add leverage and put more debt-fueled risk on their balance sheets. CBO gave Citi and JPMorgan a 50 percent chance of convincing regulators to let them take the carve-out, and their lobbyists are still working to increase that probability to 100 percent.

Factoring in the reality that the major banks will be lobbying regulators in the Trump administration could plausibly increase the likelihood of their success.

CBO’s cost estimate of S.2155, the bipartisan bank deregulation bill that faced its first test vote today, was obtained by the Washington Post on Monday and released publicly Tuesday morning. S.2155 would cost taxpayers $671 million over a 10-year period, CBO estimated, because of the increased possibility of bank failures and financial crisis from using more leverage and other deregulatory changes. “The probability is small under current law and would be slightly greater under the legislation,” they concluded.

Of course, if a crisis did occur, $671 million would seem like a pittance.

“Hardworking Americans shouldn’t have to pay for favors to Wall Street, foreign megabanks and their lobbyists,” said Sen. Sherrod Brown, D-Ohio, a leading critic of the bill, in a statement.

The CBO estimate did little to sway the 17 members of the Senate Democratic Caucus who voted Tuesday to begin debate on the bill. But it does reveal that Citigroup has already gotten halfway toward its goal of piling on more risk.

Among other parts of the bill, CBO analyzed Section 402, which would change the supplementary leverage ratio, or SLR, a simple calculation of total equity divided by total assets. The section lets “custodial banks,” which do not primarily make loans but instead safeguard assets for rich individuals and companies like mutual funds, to eliminate reserve funds parked at central banks from the calculation, reducing leverage by as much as 30 percent. This would juice returns for these banks but also layer on additional risk, by allowing them to hold less equity to offset losses in a crisis.

As first reported by The Intercept, Citi lobbyists successfully engineered a change to Section 402’s language. While the definition of a custodial bank used to stipulate that only a bank with a high level of custodial assets would qualify, it subsequently defined a custodial bank as “any depository institution or holding company predominantly engaged in custody, safekeeping, and asset servicing activities.”

Citi and JPMorgan do perform some custodial activities, though it’s not their primary business. The banks could argue that as holders of deposits, they are predominantly custodians of other people’s money. That would enable them to reduce leverage the way the nation’s primary custodial banks would — Bank of New York Mellon, State Street, and to a lesser extent Northern Trust.

“CBO estimates that regulators also may determine that other institutions would be eligible for the SLR adjustment if the value of their custodial activities is similar to that of the three traditional custody banks,” the organization writes. “For this estimate, CBO assumes that there is a 50 percent chance that regulators would allow two other financial institutions — JP Morgan and Citibank, with combined assets of $4.4 trillion — to adjust their SLRs under the terms in the bill.”

This language is identical to CBO’s analysis of H.R. 2121, a House bill that had the same SLR provision in it. The Senate language, once changed, became substantially similar to the language in the House bill.

A report from industry trade group the Clearing House does show that, while Bank of New York ($24.6 trillion) and State Street ($21.7 trillion) topped the list of custodial assets under management as of the end of 2014, JPMorgan ($21.1 trillion) held almost as much, with Citi ($12.5 trillion) trailing, though still exceeding Northern Trust’s assets ($6 trillion).

According to CBO, Section 402 would cost taxpayers $45 million over the next 10 years, a measure of the potential for failure of the custodial banks, as well as JPMorgan Chase and Citigroup. This would cost both the Federal Deposit Insurance Corporation’s Deposit Insurance Fund, as well as its Orderly Liquidation Fund, used to unwind complex banking institutions during a crisis.

In a statement Monday, Financial Crisis Inquiry Commission chair Phil Angelides cited the leverage changes as among the biggest problems with the bill, as it would “lead to a substantial reduction in required capital at certain large banks, a troubling reversal of the drive toward stronger capital requirements in the wake of the crisis. The need for enhanced capital at major financial institutions has been one of the areas of broadest consensus emanating from the 2008 meltdown.”

Section 402 is listed as one of three main changes with budgetary effects in the legislation, and since CBO equates budgetary changes in this bill with increased probabilities of bank failure, one of the three most dangerous pieces of S.2155.

Kurt Walters, campaign director at anti-corruption organization Rootstrikers, said in a statement that “the CBO’s report just destroyed any case that this bill is ‘community banking’ legislation. A neutral arbiter just confirmed that this bill would increase the risk of future bank bailouts and gave even odds that it would let Wall Street giants Citi and JPMorgan pile on more risk.”

Politico reported Monday that several other Democratic Senate caucus members beyond the 13 co-sponsors, including Amy Klobuchar, D-Minn.; Maggie Hassan, D-N.H.; Jeanne Shaheen D-N.H.; Bill Nelson, D-Fla.; and Tammy Duckworth, D-Ill., could support passage of the bill. Walters suggested: “At this point, any Democrat voting to advance this bill ought to just retire and start working directly as a lobbyist for the big banks.”

More information on S.2155 can be found in The Intercept’s feature story on the bill.

Update: March 6, 2:21 p.m.

This story has been updated to reflect that the Senate voted Tuesday to advance the banking bill.