This ground is much less plowed than the executive privilege argument commentators have been expecting Pence to raise. As I have emphasized since the subpoena was served last week, that argument should fail on the basis of several constitutional principles, chief among them the Supreme Court’s ruling, in United States vs. Nixon, that even the president’s confidentiality concerns yield to the need for specific evidence in a criminal investigation.

Moreover, federal courts in Washington have made quick work of the executive privilege arguments in recent cases involving former White House Counsel Pat Cipollone and his deputy, Patrick Philbin, and the Supreme Court has not reviewed their decisions. So an executive privilege argument might cause only a short delay in enforcement of the subpoena.

I don’t think the same quick justice is in store for the argument that Pence is raising. The contours of the speech or debate clause, which protects members of Congress from being questioned about what they say in the course of legislative proceedings, are underexplored and murky. That means the courts are likely to at least request briefing and argument and produce original constitutional analysis.

That said, I don’t think the claim will ultimately prevail. What is settled is that the speech or debate clause protects only “legislative speech” or “legislative acts.” The provision is rooted in historical efforts to protect members of the British Parliament from being cowed by threats of prosecution by the monarch. It would clearly prohibit, for example, arresting a legislator during a floor debate. On the other extreme, however, it clearly doesn’t prohibit prosecuting a legislator who takes a bribe or otherwise engages in criminal activity.

It’s hard to imagine a less “legislative” and more “executive” function of the vice president than the one-on-one conversations between Pence and Trump that are the linchpin of what the special counsel is seeking. The vice president may wear two constitutional hats, but that doesn’t mean he can put them on simultaneously. And for the purposes of the case Smith is developing, Pence was firmly in his executive branch role.

Pence also could hazard a more bare-bones argument that United States vs. Nixon doesn’t apply to an executive branch subpoena of a legislative official. Nothing in Nixon hints at that limitation, but many conservative judges have become enamored of broad interpretations of the separation of powers.

The problem here for Pence, however, is that he is no longer a legislative official. The subpoena was served on him as a private citizen.

Bottom line: Pence’s gambit should fail, but it probably won’t do so as quickly as a straight executive privilege argument. That means it could prolong the case into the heart of the 2024 presidential campaign. In that event, Smith might be forced into a choice between forgoing Pence’s testimony or conducting the first-ever prosecution of a former president in the middle of a campaign in which he is the front-runner for a major party’s nomination.

For Pence, the political calculus of delaying the case is perhaps even more important than his chances of winning his legal claim. The former vice president could likely provide devastating evidence against his former boss that could help secure federal charges against Trump and make his own path to the presidency more feasible. But with former U.N. Ambassador Nikki Haley jumping into the race Tuesday and other Republicans poised to follow suit, Pence appears to have concluded that he still needs to tow Trump’s barge lest he completely lose the 32% or so of the electorate that is inexhaustibly faithful to Trump.

And let’s not forget that Trump could still parachute into the case to raise the executive privilege argument that Pence is apparently forgoing. Indeed, since Trump is incapable of nuanced thinking and has an incorrigible, nearly biological compulsion to fight, we should expect it. The result would be to join the two men, who deeply mistrust each other and have sharply divergent interests, in a joint legal effort.

As ever, Trump and his former cohorts are taking the Justice Department, the courts and the country into new and scarcely ponderable territory — and giving rise to seemingly endless delays in holding the former president to account.