ATLANTA (AP) — The Georgia prosecutor who’s investigating whether former President Donald Trump and others illegally interfered in the 2020 general election in the state has informed 16 Republicans who served as fake electors that they could face criminal charges.

They all signed a certificate declaring falsely that then-President Trump had won the 2020 presidential election and declaring themselves the state’s “duly elected and qualified” electors even though Joe Biden had won the state and a slate of Democratic electors was certified. Eleven of them filed a motion Tuesday to quash their subpoenas, calling them “unreasonable and oppressive.”

Also Tuesday, U.S. Sen. Lindsey Graham, a South Carolina Republican, agreed to file any challenges to a subpoena in the investigation in either state superior court or federal court in Georgia, according to a court filing. He had previously filed a motion in federal court in South Carolina trying to stop any subpoena from being issued to him there on behalf of the prosecutor in Georgia.

Fulton County District Attorney Fani Willis last year opened a criminal investigation “into attempts to influence the administration of the 2020 Georgia General Election.” A special grand jury with subpoena power was seated in May at her request. In court filings earlier this month, she alleged “a multi-state, coordinated plan by the Trump Campaign to influence the results of the November 2020 election in Georgia and elsewhere.”

Willis’ office declined to comment Tuesday on the motion to quash the subpoenas.

A lawyer for Willis’s office said in a court filing Tuesday that each of the 16 people who signed the false elector certificate has received a letter saying they are targets of the investigation and that their testimony before the special grand jury is required.

In the motion to quash the subpoenas, lawyers for 11 of the fake electors said that from mid-April through the end of June, Willis’s office had told them that they were considered witnesses, not subjects or targets of the investigation. For that reason, they had agreed to voluntary interviews with the investigative team, the motion says. Georgia Republican Party Chairman David Shafer and another of the fake electors appeared for interviews in late April.

On June 1, grand jury subpoenas were sent to all 11 of those fake electors. And on June 28, the district attorney’s office told their lawyers for the first time that their clients were considered targets, rather than witnesses, the motion says.

On Dec. 14, 2020, when Georgia’s official Democratic electors met to certify the state’s electoral votes for Biden, the fake Republican electors also met to certify a slate of electoral votes for Trump. They did that because there was a lawsuit challenging the election results pending at the time, and if a judge found that Trump had actually won their electoral slate would become valid, the motion says.

The district attorney’s office knew all that and properly labeled them witnesses, prompting them to agree to voluntary cooperation, the motion says.

“The abrupt, unsupportable, and public elevation of all eleven nominee electors’ status wrongfully converted them from witnesses who were cooperating voluntarily and prepared to testify in the Grand Jury to persecuted targets of it,” the motion says. As a result, their lawyers advised them to invoke their federal and state rights protecting them against self-incrimination, and they “reluctantly” accepted that advice, the motion says.

Their lawyers assert that the change in status from witnesses to targets was based on “an improper desire to force them to publicly invoke their rights as, at best, a publicity stunt.” Therefore, they should be excused from appearing before the special grand jury, the motion says.

The motion asks Fulton County Superior Court Judge Robert McBurney, who’s overseeing the special grand jury to excuse the 11 electors from appearing before the panel. It also asks him to look into Willis’ actions “indicating the improper politicization of this investigatory process.”

And it asks him to grant a motion filed Friday by state Sen. Burt Jones seeking to remove Willis and her office from the investigation. Jones, who’s the Republican nominee for lieutenant governor, alleged that the investigation is politically motivated because Willis is an active supporter of his Democratic opponent. McBurney on Tuesday set a Thursday hearing on that motion.

Willis’s office has said Jones’ claims are without merit and a lawyer representing the office wrote in a filing Tuesday that Jones has identified no actions that show political motivation.