Former Vice President Mike Pence is reportedly planning to fight a subpoena for testimony as part of a Justice Department special counsel’s investigation into former President Donald Trump.

Multiple sources close to Pence informed Politico that the former VP, who is rumored to be planning to announce a 2024 White House run, will likely address his plans to resist the subpoena during a visit to Iowa on Wednesday.

The aides told Politico that Pence’s decision to challenge Special Counsel Jack Smith’s request has little to do with executive privilege, instead, he plans to argue that his former role as president of the Senate — therefore a member of the legislative branch — shields him from certain Justice Department demands.

Pence allies say he is covered by the constitutional provision that protects congressional officials from legal proceedings related to their work — language known as the “speech or debate” clause. The clause, Pence allies say, legally binds federal prosecutors from compelling Pence to testify about the central components of Smith’s investigation. If Pence testifies, they say, it could jeopardize the separation of powers that the Constitution seeks to safeguard.

“He thinks that the ‘speech or debate’ clause is a core protection for Article I, for the legislature,” said one of the two people familiar with Pence’s thinking, who spoke on condition of anonymity to discuss his legal strategy. “He feels it really goes to the heart of some separation of powers issues. He feels duty-bound to maintain that protection, even if it means litigating it.”

That’s because the legal question of whether the vice president draws the same “speech-or-debate” protections as members of Congress remains largely unsettled, and constitutional scholars say Pence raising the issue will almost certainly force a court to weigh in. That could take months.

“It is admittedly a constitutionally murky area with no clear outcome,” said Mark Rozell, a George Mason University political scientist who specializes in executive privilege. “Since there is a legislative function involved in the vice president presiding over the Senate, a court very well could decide that it must address the scope of the speech or debate privilege and whether it would apply in this case.”

Last week, Smith’s office moved to subpoena Pence in one of its most aggressive moves to date as its inquiries into Trump’s alleged efforts to overturn the 2020 presidential election accelerate. (RELATED: Special Counsel Overseeing Trump Criminal Probe Subpoenas Mike Pence)

Notably, the Justice Department has previously argued in civil litigation that the “speech or debate” clause protects the vice president when working on Senate business. The department explicitly asserted in 2021 that Pence was shielded by the “speech or debate” clause in a civil lawsuit related to his role presiding over Congress’ Jan. 6 session.