COLUMBIA, S.C. (AP) — 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 Graham, a top ally of Trump’s, sought to halt his possible testimony while he continues to appeal the order to appear before the Fulton County special grand jury.

Graham’s office described the South Carolina Republican’s filing as an attempt “to defend the Constitution and the institutional interest of the Senate.” The lower court’s ruling, Graham’s office said, “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. Some have already made their appearances before the special grand jury, including former New York mayor and Trump attorney Rudy Giuliani — who’s been told he could face criminal charges in the probe — attorneys John Eastman and Kenneth Chesebro, and former White House counsel Pat Cipollone.

Paperwork has been filed seeking testimony from others, including former White House chief of staff Mark Meadows, former national security adviser Michael Flynn and former U.S. House Speaker Newt Gingrich.

Graham, a four-term senator who last won reelection in 2020, was first subpoenaed in July by Fulton County District Attorney Fani Willis, who opened her investigation shortly after a recording of a January 2021 phone call between Trump and Georgia Secretary of State Brad Raffensperger was made public. In that call, Trump suggested Raffensperger could “find” the votes needed to overturn his narrow loss to Democrat Joe Biden.

Willis wants to question Graham about two phone calls he made to Raffensperger and his staff in the weeks after the election.

During those calls, Graham asked about “reexamining certain absentee ballots cast in Georgia in order to explore the possibility of a more favorable outcome for former President Donald Trump,” Willis wrote in a petition seeking to compel his testimony.

Graham also “made reference to allegations of widespread voter fraud in the November 2020 election in Georgia, consistent with public statements made by known affiliates of the Trump Campaign,” she wrote. She said in a hearing last month that Graham may be able to provide insight into the extent of any coordinated efforts to influence the results.

Raffensperger said he took Graham’s question about absentee ballots as a suggestion to toss out legally cast votes. Graham has dismissed that interpretation as “ridiculous.” Graham has also argued that the call was protected because he was asking questions to inform his decisions on voting to certify the 2020 election and future legislation.

Graham challenged his subpoena in federal court, but a judge refused to toss it out. Graham then appealed to the 11th U.S. Circuit Court of Appeals, and a three-judge panel ruled Thursday in favor of Willis. Graham can appeal to the full court.

Graham’s lawyers argued that the Constitution’s speech or debate clause, which protects members of Congress from having to answer questions about legislative activity, shields him from having to testify.

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.

Graham’s filing Friday 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 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, though no evidence has emerged that she contacted Georgia officials. 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, despite the fact that numerous federal and local officials, a long list of courts, top former campaign staffers and even Trump’s own attorney general have all said there is no evidence of mass fraud.

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