The bipartisan amendment which would transform the way the credit rating agencies do business, authored by Al Franken, got a boost today when Iowa Republican Chuck Grassley, whose voting record throughout Wall Street reform has grown more populist as he sees a legitimate challenge to his re-election at home, signed on to the amendment. From a press release from Sen. Franken’s office:

“If the credit rating agencies are going to make a contribution to market integrity, then they can’t be compromised,” said Sen. Grassley. “This amendment creates a firewall so that a rating agency can be selected independent of an issuer. It goes after conflicts of interest between rating agencies and issuers, and that’s a very important area where due diligence was missing leading up to the financial crisis of 2008.”

Grassley joins Roger Wicker (R-MS) as the two Republicans who have thus far co-sponsored the amendment. Fifteen Senators in all have co-sponsored, including Tim Johnson (D-SD), number 2 on the Senate Banking Committee and practically a bank executive himself.

As noted before, the amendment would create an office of Credit Rating Agencies inside the SEC which would assign securities to accredited rating agencies for their initial assessment. This would end the “issuer pays” model, which encouraged the rating agencies to cut corners and do deals with the banks, ensuring triple-A ratings in exchange for the promise of more business and higher fees.

With bipartisan support, the Franken amendment is among those reforms likely to pass and strengthen Wall Street reform – if it gets a vote. Democratic leaders still seem intent on wrapping up debate on the bill by the end of the week. If that happens, maybe of the hundred-plus amendments still waiting for a vote might get left out. The timing of when debate ends on this bill should not be measured by an arbitrary date, but by the time when all Senators have had the right to improve the legislation. The Franken amendment is an important example – under a 50-vote standard, which is likely, the amendment would be very likely to pass, especially if it builds more support on the Republican side of the aisle beyond Grassley and Wicker. There’s no reason to cut off debate without getting a vote on this and other measures.