A Republican Pennsylvania Supreme Court justice failed to disclose a $25,000 campaign donation from a top Republican lawmaker who is a defendant in a lawsuit challenging the states congressional map as an unconstitutional partisan gerrymander .

Justice Sallie Updyke Mundy filed an updated disclosure in the case on Monday, noting the $25,000 donation during her Supreme Court candidacy from a PAC supporting Senate President Pro Tempore Joe Scarnati. She apologized for failing to disclose the money before the Supreme Court heard the lawsuit, and said she still believes she can judge the litigation impartially.

Mundy was one of two GOP justices who disagreed when the Pennsylvania Supreme Court majority struck down the states congressional map in January and ordered a new one.

Her failure to disclose the donation, first reported by Mother Jones , is the latest in an escalating fight over the gerrymandering decision that challenges the impartiality of the justices on Pennsylvanias highest court. On Friday, House Speaker Michael Turzai (R) and Scarnati moved to disqualify the vote of Justice David Wecht, a Democrat, because he made statements against gerrymandering when he was a candidate in 2015.

Plaintiffs in the gerrymandering case wont seek to disqualify Mundys vote over the donation disclosure, said Barbara Grimaldi, a spokeswoman for the Public Interest Law Center, a Philadelphia-based group representing them.

Scarnati said in a statement Monday that he and Mundy had properly disclosed the donation from his PAC in campaign finance reports. He also said three Democrats on the Supreme Court failed to disclose contributions from a PAC supporting Gov. Tom Wolf (D), who also is a defendant in the gerrymandering case. Those justices Wecht, Kevin Dougherty and Christine Donohue also did not disclose millions in donations from labor unions that filed amicus briefs in this case, Scarnati said.

Scarnati said the push to disqualify Wecht had nothing to do with donations.

Justice Wecht and Justice Donohue promised an outcome prior to the League of Women Voters filing of the lawsuit, Scarnati said, adding, Justice Wechts numerous unequivocal statements regarding gerrymandering,, calling it an abomination on several occasions, establish that even before he was elected to the Supreme Court, his mind was made up.

Stephen Gillers, a New York University law professor and an expert on judicial ethics, said a $25,000 donation would be enough to push for Mundys recusal. But the justice wouldnt necessarily have to disclose the contribution to litigants if it had been publicly available information, he said.

The donation was included in campaign finance reports posted on the Pennsylvania Department of State website. If the information that could serve as the basis for recusal is readily available on a courts website or in financial disclosure filings, the judge can assume that the lawyers are doing their homework and know about it, Gillers said in an email.

Campaign finance reports show two Republican members of Congress from Pennsylvania Reps. Charlie Dent and Brian Fitzpatrick also made $1,000 donations to Mundys 2017 campaign, which she failed to disclose.

Munday, in a statement filed in November, did disclose a donation from Obermayer Rebmann Maxwell & Hippel. Lawrence Tabas, an attorney at the firm, represented Republican voters in the gerrymandering case.

This article has been updated to include statements from the Public Interest Law Center and Scarnati.