A reverse discrimination lawsuit filed by a group of Connecticut firefighters is shaping up to be the most contentious case in which Sonia Sotomayor participated, one sure to provoke sharp questioning when the Senate begins consideration of her nomination to the Supreme Court.

In 2008, Sotomayor was one of three judges on a panel of the U.S. Court of Appeals for the 2nd Circuit who upheld a trial court’s ruling rejecting the reverse discrimination claims by 19 white firefighters, one of whom was also Hispanic. The plaintiffs claimed that the city of New Haven violated their rights by throwing out the results of an officers’ promotion exam in which minority candidates received disproportionately low scores.

The substance of that 2008 ruling, which the Supreme Court is now considering, is proving less problematic than the manner in which Sotomayor and the other two judges on her panel handled the case.

At first, they issued only a brief, unsigned summary order noting the trial court’s “thorough, thoughtful, and well-reasoned opinion” rather than offering a full opinion of their own. Four months later, as the full circuit court was about to issue a ruling on whether to take up the case, they withdrew the unpublished order and issued an equally brief unsigned opinion.

The full court voted not to review the case but Judge Jose A. Cabranes wrote a dissent in which he suggested that Sotomayor’s panel “failed to grapple with the questions of exceptional importance raised in this appeal.”

The case, Ricci v. DeStefano, is only going to attract more attention in the runup to Sotomayor’s confirmation hearing. The Supreme Court has already heard oral arguments and is sure to release its decision by early July — before the Senate is likely to vote on Sotomayor’s nomination. She is almost certain to be grilled at her confirmation hearing before the Senate Judiciary Committee about how she handled the case.

Already, conservatives have seized on the dissent by Cabranes, an appointee of President Bill Clinton, to make the case that Sotomayor and her colleagues were trying to bury the case and make it less likely the Supreme Court would review the claims of reverse discrimination.

“Why proceed this way unless you’re trying to prevent review of these claims?” said Ed Whelan, president of the conservative Ethics and Public Policy Center.

On a conference call Wednesday organized by the White House, several law professors and appellate attorneys defended how Sotomayor and her two colleagues handled the matter.

“The notion you’re going to hide an opinion is pretty much nonsense,” said Bill Marshall, a law professor at the University of North Carolina.

Obama administration officials have tried to put a positive spin on the way Sotomayor handled the case, suggesting it is actually evidence of her respect for precedent and judicial restraint. That message was echoed in the White House’s conference call.

“She was part of a panel that decided they were bound by previous 2nd Circuit decisions, which meant they couldn’t make new law,” Marshall said.

But Cabranes appeared to undermine the suggestion that the issues in the case were well-settled law when he wrote in his dissent, “This appeal raises important questions of first impression in our circuit — and indeed, in the nation regarding the application of the 14th Amendment’s Equal Protection Clause and Title VII’s prohibition on discriminatory employment practices.”