Donald Trump's impeachment is headed to the U.S. Senate, where Chief Justice John Roberts will preside over the trial.

The Senate will serve as a jury, and the Constitution requires them to do so "on oath or affirmation." The Senate Rules spell out the oath they must take, which calls for them to do "impartial justice according to the Constitution and the laws."

Some senators are clearly unfit to try this case, and must be disqualified, if they will not recuse themselves:

• Senate Majority Leader Mitch McConnell (R-KY) has openly admitted that he's not an impartial juror, and has even strategized behind closed doors with Donald Trump's legal time to map out the trial—with the desired outcome of his eventual acquittal.

• Senator Lindsey Graham (R-SC) won't even pretend to be a "fair juror," and has said he wants impeachment to "die quickly" in the Senate with no witnesses.

• Senator Ron Johnson (R-WI) was a witness in various incidents that relate to the underlying charges against Donald Trump. But he insists that he will not recuse himself, because this is a "political process," not a judicial trial.

Given these statements, Senators McConnell, Graham & Johnson would have to commit perjury in order to be seated in this impeachment trial.

Senators McConnell, Graham & Johnson have all disqualified themselves—and will taint the outcome of any verdict that acquit Trump. And lower respect for our institutions. As Justice Roberts himself recently said: "we have come to take democracy for granted."

Sign the petition to Justice John Roberts: Disqualify senators who refuse to hold a fair impeachment trial.