Pence and his lawyers intend to cite constitutional grounds as they prepare to resist Special Counsel Jack Smith‘s efforts to compel his testimony before a grand jury.

They argue that because Pence was serving in his role as president of the Senate on January 6, 2021, he is protected from being forced to address his actions under the Constitution’s “speech-or-debate” clause, which shields members of Congress.

Pence was presiding at the time over a joint session of Congress to certify the 2020 election results.

“I think he views it as essential protection of his Constitutional role,” said Marc Short, a close adviser to Pence who served as his White House chief of staff.

Short compared Pence’s position to the one he took on January 6, when he refused to go along with Trump’s unconstitutional scheme to try to overturn the results of the 2020 election, as well as Pence’s rejection of using the 25th Amendment to remove Trump from office in the aftermath.

“The vice president of the United States is the president of the Senate, and the fact is the functions of January 6 were specific to that role,” he said of Pence, who has been laying the groundwork for a likely presidential campaign that would put him in direct competition against his former boss.

Whether Pence’s arguments will succeed in limiting or altogether avoiding grand jury testimony is unclear. But the US Justice Department is expected to oppose those efforts and make the case that the former vice president’s cooperation is essential for the probe.

The decision to try to fight the subpoena, first reported by Politico, marks a change in posture from Pence. He has previously cooperated with the Justice Department as it investigates how documents with classified markings ended up at his Indiana home. He also permitted the Federal Bureau of Investigation (FBI) to search the property last week.

Even if his objection is ultimately rebuffed by the courts, an antagonistic posture could allow Pence to argue that he tried to fight the Justice Department — a potentially useful position in a Republican primary, as many in the party’s base have grown distrustful of federal law enforcement, in part due to Trump’s drumbeat of criticism. And it could delay the special counsel probe, which Smith is working to advance rapidly.

Pence has spoken extensively about Trump’s pressure campaign urging him to reject President Joe Biden’s victory in the days leading up to January 6, including in his book So Help Me God. As vice president, Pence had a ceremonial role overseeing the counting of the Electoral College vote but did not have the power to affect the results.

Pence’s decision to resist the subpoena also comes after extensive back-and-forth talks between his lawyers and the special counsel’s office, according to a person familiar with the meetings who spoke on condition of anonymity to discuss the closed-door negotiations.

The Justice Department declined to comment on Tuesday about Pence’s plans.

Pence is expected to address the issue in more detail during a visit to Iowa on Wednesday as he inches closer to a likely presidential run.

Richard Levy, a constitutional law professor at the University of Kansas, said it is true that the vice president is in a unique position as the technical presiding officer of the Senate, making the officeholder in some respects a member of the chamber.

But he said that not everything a member does is protected by the speech-or-debate clause, and it is debatable whether the vice president’s role in certifying the election, which involves a mix of constitutional and senatorial functions, would be protected.

In any event, Pence’s argument would likely serve to limit the scope of his testimony rather than to block it altogether, he said.

“I don’t think the speech or debate clause would be a basis for quashing the subpoena altogether. It would be a basis for objecting to particular questions,” he said.

The subpoena has been an aggressive step from Smith as he continues to investigate efforts by Trump and his allies to remain in power, including the storming of the Capitol building on January 6, 2021.

Trump supporters, driven by the lie that the election was stolen, brutally pushed past the police and smashed through the windows and doors while Pence was presiding over the certification of Biden’s victory. The vice president was steered to safety with his staff and family as some in the mob chanted, “Hang Mike Pence!”

While the mob was in the Capitol, Trump tweeted, “Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution.”

A House committee investigating the January 6 attack recommended that the Justice Department bring criminal charges against Trump and others over his efforts to overturn his 2020 election loss.