Justice Prosser, a former Republican leader of the State Assembly, had been accused by union supporters of being a sure vote for anti-union measures and other efforts by the Republican-dominated Legislature and the new governor, Scott Walker, a Republican. Justice Prosser said he had shed his partisan leanings in more than a decade on the state Supreme Court, and could not be lumped as the decisive conservative vote in what many have come to see as a predictable 4-to-3 conservative-liberal split.

Justice Prosser narrowly won re-election in April. And by this month, the court was hearing arguments in perhaps the most polarizing case of all: whether Governor Walker’s bill to cut bargaining rights and benefits for public workers had been passed in a legal manner. A lower court found that Republican lawmakers violated the state’s open-meetings provisions, but on June 14 the Supreme Court decided to reinstate the law. The vote: 4 to 3, along the conservative-liberal lines that many had expected.

Justice Prosser was with the majority, who cited the importance of the separation of powers and said the State Legislature had not violated the state’s Constitution when it relied on its interpretation of its rules and gave slightly less than two hours’ notice before meeting and voting for the collective bargaining rights cuts. Justice Bradley was among the dissenters, a group that also included Chief Justice Shirley S. Abrahamson.

In her dissent, Chief Justice Abrahamson criticized Justice Prosser’s writing on the matter, saying, “It is long on rhetoric and long on storytelling that appears to have a partisan slant.”

In his re-election campaign, Justice Prosser acknowledged an earlier verbal run-in with Chief Justice Abrahamson in which he had, he said, called her a “total bitch.” In an interview with The New York Times, he explained his comments: “Did I say something I shouldn’t have said? Of course. Do I regret it? Of course. Do I apologize for it? Yes, I do.”

But in the interview, Justice Prosser also described great tension on the court. At least one of the justices had been recruiting candidates to run against him, Justice Prosser said.

“All of these things were coming to a head,” he said. “The members of the court were very, very deeply divided.”