If it’s already clear that the witnesses whom the president has successfully silenced thus far, despite their firsthand knowledge of what he knew and when he knew it in the context of shaking down Ukraine for his personal benefit, are indeed likely to be called, why take the trouble of saying more about the need for them to appear in the impeachment trial? Why say more about the need for them to give sworn testimony, notwithstanding the president’s continuing, and obviously suspicious, invocation of various “executive privileges” to silence them for the supposed benefit of future presidents ?

The case for calling witnesses in the Senate’s impeachment trial of President Trump, and for subpoenaing documents that the White House has withheld from Congress, is now too compelling to deny. There is so much public support for hearing all the relevant evidence, and not just among Democrats, that it is becoming politically toxic for increasingly many senators to resist doing so. Senate majority leader Mitch McConnell’s efforts to bury the truth and turn the trial into a whitewash with a quickly delivered foreordained conclusion have all but come to naught, thanks in large part to the patience and savvy of House Speaker Nancy Pelosi, who wisely resisted the pressure to transmit the two articles of impeachment within days of the House vote impeaching Trump.


The reason is that we cannot afford to leave any stone unturned when dealing with as lawless and fickle a presidential administration and its Senate accomplices as the Trump/McConnell cabal has shown itself to be. Various senators have indicated their supposedly deep concern with what looks like a coverup — and then, when push came to shove, turned their backs on digging for the truth and instead tied their fate to Trump.

As many have observed, senators sitting in an impeachment trial are required by Article I, Section 3 of the Constitution to “be on Oath or Affirmation,” which is separate from the oath they took upon assuming their office. That special oath, ever since the impeachment trial of Andrew Johnson in 1868, has required every senator to commit, on pain of perjury, to “do impartial justice.” What that oath demands is nothing superhuman. The great French philosopher Blaise Pascal once wrote, “People almost invariably arrive at their beliefs . . . on the basis of what they find attractive.” As Joshua Matz and I explained in our book on the subject, “Impartiality has a distinctive meaning in [the] context” of a Senate trial of a sitting president. “Nearly everyone voting on his fate will identify as his ally or opponent. To demand perfect neutrality in that circumstance would be to ask the impossible.”


That said, it’s still “helpful to ask how we would answer questions if we had opposite feelings about the president threatened with removal,” we wrote. That much we surely can expect from senators. We can expect them to pay full attention to what John Adams reminded us: “Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passions, they cannot alter the state of facts and evidence.”

Indeed, that is one of the principal reasons the Framers chose the Senate rather than the Supreme Court as the trial body. They believed that no senator would be as beholden to the president as the president’s own appointees to the Supreme Court. They knew that justices, unlike senators, might be influenced by the prospect of later having to sit in judgment on appeal from a criminal conviction by an impeached and removed president prosecuted for his misdeeds after being expelled from office. And they supposed — maybe a bit too optimistically — that the Senate, being composed by and large of more seasoned and principled characters than the typical government body, could be counted on to perform the admittedly difficult task of setting bias and preconceptions aside in ruling on issues of fact and law raised by articles of impeachment presented by the House.


Some otherwise astute observers have speculated that, because the Framers thought a body with as few members as the Supreme Court would be easier to corrupt than a more populous body like the Senate, expressions of bias in advance of trial, whether by the president’s friends or by his foes, must largely be disregarded because, if “we excluded every senator who showed bias, so many would be disqualified that the trial would take place before a relatively small number.” But that misstates the issue. Nobody would propose excluding “every senator who showed bias” in a context where “bias” is ubiquitous and even unavoidable.

But showing bias and thereby confessing that one’s mind is not a blank slate that is as open to one outcome as to its opposite is one thing; acting to confirm that one’s mind is entirely closed and uninterested in hearing relevant and potentially decisive evidence — as McConnell has done — is quite another. That is where the matter of deliberately deciding not to subpoena key witnesses or documents becomes crucially linked to the oath of impartiality. To admit one’s predispositions on a question of whether the president has done something unforgivably evil in terms of his or her oath of office is merely to confess one’s humanity; but to take a “see no evil, hear no evil, speak no evil” posture with respect to any president, whether of one’s own party or not, is to establish that one is committing perjury when swearing to the chief justice of the United States and to the world that one will strive to do “impartial justice.”


This, in the end, is the strongest reason senators who take seriously the solemn oath that Chief Justice John Roberts will administer to them at the outset of the forthcoming impeachment trial cannot in good conscience, whatever the political fallout, vote not to hear and see all the evidence that would shed light on whether and how this president abused the powers entrusted to him by the American people. Senators must deliberate whether Trump continuing in office is consistent with the security of the United States and the survival of America’s separation of powers, commitment to the rule of law, and fidelity to democratic principles. And senators must weigh what precedent would be set for all future presidents were they to excuse, on the basis of affinity for his policies, his judicial appointments, or his capacity to help them retain their senatorial positions, what appear to be this president’s violations of law and his misuse of his official powers with respect to congressional appropriations and military assistance to a beleaguered ally.


By voting in favor of calling witnesses and demanding documents, Democrats will necessarily take the chance that the information revealed will help exonerate the president. If that turns out to be the case, so be it. At stake is not how best to achieve a preordained partisan result, but how best to conduct a fair trial. As Sir Winston Churchill once said, “Truth is incontrovertible. Malice may attack it and ignorance may deride it, but, in the end, there it is.”

Laurence H. Tribe is university professor and professor of constitutional law at Harvard and coauthor, most recently, of “To End A Presidency: The Power of Impeachment.” Follow him on Twitter @tribelaw.