On this week’s Amicus, Dahlia Lithwick spoke with Walter Dellinger, former acting solicitor general and emeritus professor at Duke Law School (and occasional Slate contributor). The two talked about all things impeachment, and the whole episode is worth a listen, but we’ve excerpted one of Dellinger’s answers here, edited lightly for clarity.

Dahlia Lithwick: Regardless of what we’re calling it today, Walter, whether it originated in the Judiciary Committee or in Nancy Pelosi’s statement, is it fair to assert that the impeachment process has begun?

Walter Dellinger: The impeachment process has begun. Be careful, though—a slight majority of the House membership has said they support beginning the impeachment proceedings. They have not yet committed to how they would vote on any article of impeachment.

Good clarification—this is why we pay you the big bucks, Walter. Now, my second just-clarifying question: Can Mitch McConnell just decide that he refuses to hold a trial in the Senate?

Yeah, that is a good question. We’ve only had two Senate trials of presidents: That is Andrew Johnson, who was undercutting the Civil War victory, and Bill Clinton, who lied in a deposition about his sexual relationship with an intern. We’ve only had those two, so we have very little in the way of precedents. There’s virtually no case law, except case law that says that the court is going to stay out of the substance of these issues and leave it all to Congress. The big question is, is it true that McConnell can, I think the current term is, “Garland” the impeachment process? That is to say, ignore the House’s articles of impeachment the way he had a majority of the Senate simply ignore the fact that the president of the United States had made a nomination to the Supreme Court? I tend to think the answer is that it’d be very hard for him to avoid a roll-call vote.

Because what few people realize is that in the case of the impeachment of the president, the presiding officer is the chief justice. Now, that’s actually quite important. There are 53 Republicans, but it’s normally thought that you needed more than three Republicans to come over on any vote in the Senate because Vice President [Mike] Pence would break the tie. Now, Vice President Pence is not going to be there to break the tie. So, while it takes two-thirds of the Senate to convict on articles of impeachment, it only takes a majority to pass on rulings of the chair.

And if you think about the number of senators who are from states where they’re just not solidly committed to the protection of Donald Trump at any cost, you’ve got Sen. Romney, who has already been critical of what President Trump has done. You’ve got Susan Collins, who is up for election in a moderate state. You’ve got the senator from Colorado, Cory Gardner. You’ve got a pretty moderate senator from North Carolina—two, in fact, [Thom] Tillis and [Richard] Burr, who’s been a fair chair of the Intelligence Committee. You only need three of those to have a 50–50 tie on a procedural question to be ruled on by the vote of the chief justice and the chair. That’s important because if a well-thought-out, well-crafted article of impeachment supported by nearly incontrovertible evidence—including in the most recent case, the actual assertions by the president himself—comes over, it’s unclear to me who decides when to convene the Senate, since the chief justice is the presiding officer.

When an article of impeachment is voted on, the House appoints House managers who present the articles of impeachment to the Senate and who would notify the chief justice. The House managers would propose a briefing schedule and debating schedule. The president’s attorneys would have their own counter briefing schedule, and the chief justice, I think, would confer with, certainly, the majority and minority leaders in the Senate about when it would be convenient. But it’s not clear to me that it’s Mitch McConnell rather than John Roberts, chief justice, who decides to commence the proceedings. Now, political friends tell me that Majority Leader McConnell would wish to avoid a roll-call vote. He’s got too many members who might be exposed that time either to say, “What is clearly established to have happened didn’t happen,” or to acknowledge that it happened, but say, “It’s OK for a president to do things like those that are detailed in articles of impeachment.” I don’t think the majority leader can make motions. It has to be that the president’s lawyers could move to dismiss without any further proceedings and avoid the Senate trial.

So, on that motion to just simply dismiss all the charges—which I believe they could make—if it were carried by a majority vote, I believe that’s the end of the matter in the Senate, as a matter of the Senate’s sheer power to try impeachments. But I think that the chief justice would call the question and listen to the ays and nays, and almost certainly they would be close-enough ays and nays that the chief justice would say, “The voice vote being inconclusive, the clerk shall call the roll.” Senators would have to vote without hearing any evidence, or testimony, or briefing, or presentation, and I think that would be a tough vote, particularly since the chief justice would have the vote to decide whether to proceed or not. The framers didn’t contemplate that there would be a political party that had one member that could control how every member of that party voted—that is the present system where McConnell controls his caucus. But with the chief justice in the chair, I am not at all confident that the majority leader of the Senate can successfully make this go away without having at least an initial vote.

Listen to the rest of the episode here: