The Senate impeachment trial of President Donald Trump will reconvene on Friday afternoon to consider, finally, the question of witnesses.

On Thursday, Sen. Lamar Alexander (R-TN) indicated that he would not vote for witnesses. That fueled speculation of a potential 50-50 tie in the Senate vote. If that happens, it is possible that Chief Justice John Roberts could be called upon to cast the tie breaking vote for witnesses.

Typically, Vice President would cast a tie breaking vote in the Senate — but not in impeachment trials. As the New York Times noted earlier this week, there is precedent for the Chief Justice to cast tiebreaking votes; he did so twice in the impeachment trial of President Andrew Johnson in 1868 (though on relatively minor motions to adjourn). There is also precedent for the Chief Justice to abstain, and allow a 50-50 motion to fail.

Given his restrained demeanor throughout the trial, Chief Justice Roberts could choose to abstain from any highly controversial votes.

But if he decides, as he did in the infamous Obamacare case, to make a crucial decision at conservatives’ expense, then he could cast his vote in favor of witnesses.

That would not exhaust the matter, because some of the targets of subpoenas would certainly contest those subpoenas in court.

And that would add an additional wrinkle.

The controversy would start in the federal district court. Whatever decision emerges would be appealed by either side to the U.S. Court of Appeals for the District of Columbia. And that decision would be appealed to the U.S. Supreme Court.

But Chief Justice Roberts would have to recuse himself, because of his role in making the original ruling to subpoena witnesses in the first place.

That would turn a 5-4 conservative majority into a temporary 4-4 conservative-liberal deadlock.

Assuming the justices vote in their customary blocs, the Supreme Court would split, reaching a deadlocked decision. And if that happens, the ruling of the lower, appellate court — the D.C. Circuit — will stand.

That court was stacked by President Barack Obama. And the chief judge of that court happens to be Judge Merrick Garland.

Garland was nominated by President Obama to fill the vacancy on the Supreme Court caused by the untimely death of Justice Antonin Scalia in 2016. But Senate Majority Leader Mitch McConnell (R-KY), citing the “Biden rule” — a phrase that came up again Thursday in the Senate, in connection with witnesses — blocked Garland’s Senate confirmation process from moving forward in the year before a presidential election.

McConnell’s gamble worked out when Trump won the 2016 election, and promptly appointed Justice Neil Gorsuch. Democrats have never forgiven McConnell for that, and their rage has fueled subsequent judicial confirmation fights.

Judge Garland seemed to take his disappointment in stride. But he might enjoy the opportunity to exact his revenge from McConnell and the Republicans who denied him a place on the Court.

So the irony is that if Chief Justice Roberts has the chance to weigh in on a 50-50 tie over witnesses, the final adjudication could be made not by the Supreme Court, but by Judge Merrick Garland.

Democrats would love that, and Republicans would hate it. The country would likely become even more divided. For that reason alone, Roberts is unlikely to vote.

But in a bizarre impeachment over a phone call, anything is possible.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.