Sen. Lindsey Graham, represented by former Trump White House counsel Don McGahn, asked the U.S. Supreme Court on Friday to block an order requiring him to testify before a Georgia special grand jury until his appeal to the full U.S. Court of Appeals for the Eleventh Circuit is resolved.

The grand jury is investigating whether then-President Donald Trump and others illegally tried to overturn the 2020 presidential election in Georgia. An Eleventh Circuit panel unanimously ruled on Thursday that Graham, a Republican senator from South Carolina, must testify, and affirmed a district court decision to narrow the scope of questions that prosecutors may ask him.