COLUMBIA, S.C. — U.S. Sen. Lindsey Graham on Friday asked the U.S. Supreme Court to intervene after a lower court ordered him to testify before a special grand jury in Georgia investigating whether then-President Donald Trump and others illegally tried to influence the 2020 election in the state.

In a filing with the court, attorneys for the South Carolina Republican sought to halt Graham’s possible testimony while he continues to appeal the requirement to appear before the Fulton County special grand jury.

Sen. Lindsey Graham, R-S.C., speaks with reporters on Capitol Hill in Washington, March 16, 2022.  Alex Brandon/Associated Press. file

Saying the filing was “to defend the Constitution and the institutional interest of the Senate,” Graham’s office said he was seeking to overturn a ruling that “would significantly impact the ability of senators to gather information in connection with doing their job.”

The legal move is the latest in Graham’s ongoing fight to prevent his testimony in a case that has ensnared allies and associates of the former president.

A three-judge panel of the 11th U.S. Circuit Court of Appeals had ruled Thursday in favor of Fulton County District Attorney Fani Willis, who wants to question Graham about phone calls he made to Georgia Secretary of State Brad Raffensperger in the weeks after the election.

Raffensperger said Graham asked whether he had the power to reject certain absentee ballots, something Raffensperger took as a suggestion to toss out legally cast votes. Graham has dismissed that interpretation as “ridiculous.”

Graham had challenged his subpoena, saying his position as a U.S. senator protected him from having to testify in the state investigation. He has also denied wrongdoing. The judges on Thursday rejected Graham’s argument, saying he “has failed to demonstrate that this approach will violate his rights under the Speech and Debate Clause.”

Graham is represented by former White House counsel Don McGahn, who was involved in a lengthy court fight over a congressional subpoena for his own testimony related to special counsel Robert Mueller’s investigation of Russian interference in the 2016 election. After years of back-and-forth, the two sides reached an agreement and McGahn answered investigators’ questions in a private session.

The filing was directed to Justice Clarence Thomas, who handles emergency appeals from Georgia and several other Southern states. Thomas can act on his own or refer the matter to the full court.

Trump’s lawyers recently submitted a Supreme Court application to Thomas asking the Supreme Court to step into a legal fight over the classified documents seized during an FBI search of Trump’s Florida estate.

Thomas has previously come under scrutiny for his vote in a different Trump documents case, in which he was the only member of the court to vote against allowing the House committee investigating the Jan. 6, 2021, Capitol riot to obtain Trump records held by the National Archives and Records Administration.

Thomas’ wife, Virginia “Ginni” Thomas, is a conservative activist and staunch Trump supporter who attended the Jan. 6 “Stop the Steal” rally on the Ellipse and wrote to then-White House chief of staff Mark Meadows in the weeks following the election encouraging him to work to overturn Biden’s victory and keep Trump in office.

She also contacted lawmakers in Arizona and Wisconsin in the weeks after the election. Thomas was recently interviewed by the House committee investigating the Jan. 6 insurrection, and she stood by the false claim that the 2020 election was fraudulent.

Mark Sherman in Washington contributed to this report.