Justice Clarence Thomas, in a break from his practices in earlier cases involving the 2020 election, recused himself on Monday when the Supreme Court turned down an appeal from John Eastman, a conservative lawyer who advised President Donald J. Trump on a plan to subvert the vote.
As is its custom, the court gave no reasons for denying review, and there were no noted dissents. Justice Thomas, for whom Mr. Eastman had served as a law clerk, offered no explanation for his decision to disqualify himself from the case. The justice’s wife, Virginia Thomas, known as Ginni, had participated in efforts to overturn the election.
Mr. Eastman’s petition was viewed as a long shot. It elicited no response from any other party, and Mr. Trump did not file a brief in the case.
Justice Thomas took part in a ruling last year on an emergency application from Mr. Trump asking the court to block the release of White House records concerning the Capitol attack. The court rejected the request. Only Justice Thomas noted a dissent, giving no reasons.
He also participated in the court’s consideration of whether to hear a related appeal. The Supreme Court refused to hear the case, without noted dissent. There was no indication that Justice Thomas had recused himself.
In December 2020, Justice Thomas participated in a ruling on an audacious lawsuit by Texas asking the court to throw out the election results in four battleground states. The court rejected the request, with Justices Thomas and Samuel A. Alito Jr. issuing a brief statement suggesting the majority had acted too soon in shutting down the case.
In the case the court rejected on Monday, Mr. Eastman had asked the justices to wipe out a lower-court ruling that allowed a now disbanded House committee to see emails that he said were protected by attorney-client privilege. A federal trial judge said the privilege did not apply, citing an exemption to it for crimes and fraud.
The committee, which investigated the Jan. 6 attack on the Capitol, obtained and disclosed the contested emails.
The case was thus in important ways moot, but Mr. Eastman said the rulings had damaged his reputation and that of Mr. Trump.
“The crime-fraud ruling of the district court imposes a stigma not only on petitioner,” the petition said, “but also on his former client, the former president of the United States and current candidate for the presidency in 2024.”
In a ruling last year in a lawsuit over whether the committee could obtain the emails, Judge David O. Carter ruled that it was more likely than not that the communications involved crimes, prompting the exception to the attorney-client privilege.
“The illegality of the plan was obvious,” he wrote. “Our nation was founded on the peaceful transition of power, epitomized by George Washington laying down his sword to make way for democratic elections. Ignoring this history, President Trump vigorously campaigned for the vice president to single-handedly determine the results of the 2020 election.”
The judge added, “Based on the evidence, the court finds it more likely than not that President Trump corruptly attempted to obstruct the joint session of Congress on Jan. 6, 2021.”