Vice President Pence says he will not endorse President Trump but may soon take the witness stand to testify about the 45th president’s alleged efforts to overturn the results of the 2020 election after Trump unsuccessfully urged him to refuse to certify the election.

Pence, who ran unsuccessfully against Trump for the Republican nomination this year, told Fox News in March: “It should come as no surprise to anyone that I will not be supporting Donald Trump.” He added that the “issue of loyalty to the Constitution is no small matter” and accused the former president of “turning away” from the national constitution.

The former vice president has long been a key figure in the criminal case. Trump against the United Statesfiled by special counsel Jack Smith for the events of January 6, 2021. The indictment is dominated by interactions between Trump and Mr. Pence, who was tasked with certifying President Biden’s victory. Those conversations are likely to be the subject of fierce litigation following the Supreme Court’s landmark immunity ruling.

The 6-3 decision, written by Chief Justice Roberts, says presidents are presumptively immune for their official acts, have absolute immunity for acts within their “sole and exclusive” authority, and are not immune for unofficial acts. The justices have sent the case to District Judge Tanya Chutkan for hearings to determine which acts fall into which category in the indictment against Mr. Smith. That trial begins next month and could include sworn testimony from Mr. Pence.

Mr. Pence describes some of what happened between the two men on that fateful day in his memoir, So Help Me God. Speaking at the Ellipse in Washington, Trump told the crowd regarding the certification of the election: “I hope Mike will do the right thing. I hope so. I hope so. Because if Mike Pence does the right thing, we will win the election.”

The vice president had previously told the president, “We both swore an oath to support and defend the Constitution,” and announced that he would certify the results. Some of those storming the Capitol chanted, “Hang Mike Pence.”

Could Mr Pence help Mr Smith convict Trump? The Supreme Court in Trump ruled that “the allegations that Trump attempted to pressure the Vice President to take certain actions in connection with his role in the certification process … constitute official conduct, and Trump is at least presumptively immune from prosecution.” That means Mr Smith faces a high – though not insurmountable – hurdle if he hopes to bring the conversations between Mr Pence and Trump to court.

The first step in doing so could be to subpoena Mr. Pence to testify in one of the immunity mini-trials that will take place before Judge Chutkan this fall. This follows the Supreme Court’s order that all questions about presidential privileges in criminal prosecutions must be resolved before a jury trial begins. If he does so, it would not be the first time the former vice president has testified in connection with the criminal case against the 45th president.

Mr. Pence spoke for more than five hours to the District of Columbia grand jury that indicted Mr. Trump at Mr. Smith’s behest. Initially, Mr. Pence refused to testify, basing his constitutional challenge to his subpoena on the Speech or Debate Clause of the Constitution, which provides that lawmakers “shall in all cases … be immune from arrest while attending the session of their respective Houses, and in their way thereto, and in their return from the same; and that they shall not be questioned in any other place for any speech or debate in either House.”

That privilege, based on old protections in Congress, is absolute as long as a legitimate legislative purpose is invoked. To invoke that protection, Pence invoked the Constitution’s edict that “the Vice President of the United States shall be President of the Senate.” Such an argument had never been made before, but a judge found that certain conversations between Pence and Trump were protected but others were not. Pence declined to appeal the judge’s ruling and testified.

That ruling is under seal, so the scope of the privilege is not exactly known. Any appearance by Mr. Pence before Judge Chutkan would likely require Mr. Smith to consider both presidential immunity and the speech or debate privilege. But the special counsel may think the effort is worth it – he claims that Mr. Pence’s role was “fundamental to the United States democratic process and, until 2021, it functioned peacefully and orderly for more than 130 years.”

It is now up to Judge Chutkan to decide, in the words of Chief Justice Roberts, “whether a prosecution related to Trump’s alleged attempts to influence the Vice President’s oversight of the certification process risks impairing the authority and functions of the Executive Branch.” This means that Mr. Pence once again finds himself at the center of a constitutional dilemma of no his own making.