The plaintiffs lawyers behind last month’s $7 billion class settlement over credit card swipe fees must have expected to hit some bumps on the way to getting the record-breaking antitrust deal approved. But at the rate named plaintiffs are defecting to a breakaway camp led by Constantine Cannon, the proposed settlement–at least in its current form–may be headed straight for a cliff.

Co-lead plaintiffs counsel at Robins Kaplan Miller & Ciresi; Berger & Montague; and Robbins Geller Rudman & Dowd announced on July 13 that they’d secured an agreement from Visa and MasterCard and their partner banks to pay an estimated $7.2 billion over claims that they fixed the interchange fees that merchants pay for credit and debit card transactions. But before the parties even filed the settlement agreement in Brooklyn federal district court, named plaintiff National Association of Convenience Stores hired Constantine Cannon to contest the deal, prompting the trio of co-lead plaintiffs firms to withdraw their representation of NACS.

Now the same sequence has been repeated with three more of the 19 proposed class representatives in the case. On July 27 Constantine Cannon filed a notice of appearance for the National Grocers Association. On Aug. 1 the same thing happened with the National Community Pharmacists Association, and on Monday the National Cooperative Grocers Association joined the Constantine Cannon breakaway camp.

U.S. Magistrate Judge James Orenstein in Brooklyn granted the co-lead plaintiffs firms’ requests to withdraw as counsel for all four class representatives. Orenstein has scheduled a status conference for Thursday morning, setting the stage for what should be an interesting first meeting between the defectors’ lawyers at Constantine Cannon and the remaining plaintiffs’ counsel at Robins Kaplan, Berger & Montague, and Robbins Geller.

The objectors’ main beef with the settlement is that it amounts to a drop in the bucket compared with the massive fees merchants are charged for credit card transactions, and at the same time would force them to waive their rights to pursue further litigation. But K. Craig Wildfang of Robins Kaplan told us it was revealing that only trade association plaintiffs are contesting the deal so far. (Both Wal-Mart and Target have also opposed the settlement, but they aren’t among the named plaintiffs in the consolidated case.)

“The class representatives who are actual merchants are supporting the settlement,” Wildfang said, adding that the trade associations may have political or legislative agendas that don’t always match the financial interests of the individual merchants.

Jeffrey Shinder of Constantine Cannon called that notion “absolutely false.” Each of the trade associations that have opposed the deal so far are governed by their members, he said, “and the fact that their boards all voted unanimously to oppose this deal should speak volumes.”

“As this process plays out it will be clear to everyone that the trade associations that are coming out against this deal are closer to the true interests of the merchant community and the class than those who support the deal,” Shinder said. “I wouldn’t be surprised if there are additional defectors given scope of dissatisfaction with this settlement.”