In a floor speech Tuesday, Senate Majority Leader Mitch McConnell, R-Ky., suggested that he might well prefer a perfunctory mini-trial with no live witnesses on the two impeachment articles against President Donald Trump, ripping the House impeachment inquiry as “slapdash” and the “least thorough” in history. "It is not the Senate's job to leap into the breach and search desperately for ways to get to guilty," he added.

Of course, the Republicans want the impeachment trial to be a nonevent. A quickie, minimalist Senate trial would ensure that no additional damaging evidence about the president’s actions could surface. It would also produce dismal television ratings and bolster the Republican talking point that the impeachment evidence is thin and incomplete by making sure that the evidence is as thin as they can make it.

But both Senate history and political pressure on McConnell — who is running for re-election in 2020 — will test his willingness to short-circuit a Senate trial.

The impeachment trial of a president necessarily takes time: An impeachment trial of a president is a rare and grave constitutional proceeding warranting adequate time and the full attention of the Senate. President Andrew Johnson’s trial lasted more than two months, from March 5 to May 15, 1868, and President Bill Clinton’s trial lasted five weeks, from Jan. 7 to Feb. 12, 1999 — even though the basic facts were uncontested.

The American people — and history — are entitled to a full and fair hearing of the grave charges that Trump has engaged in an abuse of power endangering our national security and in blatant obstruction of the congressional impeachment inquiry.

McConnell’s statements Tuesday about the possible format of a Senate trial came after Minority Leader Chuck Schumer, D-N.Y., on Sunday demanded what the seriousness of the impeachment charges deserves: A thorough and complete airing of the evidence supporting both articles of impeachment, including testimony from former national security adviser John Bolton and White House chief of staff Mick Mulvaney, who refused to comply with an invitation and a subpoena, respectively, to testify before the House. (McConnell seemed to reject Schumer’s demands, likening it to “jurors… brainstorming witness lists for the prosecution” and “new fact-finding.”)

But the language of the two impeachment articles requires the testimony of new witnesses, alleging that Trump engaged in a “pattern” of obstruction and abuse of power which assuredly includes 10 incidents of potential obstruction of justice listed in former special counsel Robert Mueller’s final report. This will necessitate further proofs beyond what the House Intelligence Committee heard.

And Senate rules adopted in 1986 for conducting an impeachment inquiry reinforce the value of a comprehensive trial with witnesses, both those willing to testify and those coerced by Senate-issued subpoenas. The 1986 version of the Senate impeachment rules state: “The Senate shall have power to compel the attendance of witnesses.” These orders can be enforced by the Senate’s Sergeant at Arms “who may employ such aid and assistance as may be necessary” to enforce its orders and writs.

In the impeachment of Clinton in 1999, the Senate adopted two resolutions — Senate Resolutions 16 and 30 — amending these impeachment rules. These changes allowed new witnesses to be subpoenaed for videotaped depositions, though they specified that no witness would be allowed to testify at trial unless that witness previously had been deposed.

Further, while Chief Justice John Roberts — who will preside over the Senate impeachment trial — is authorized to issue requested subpoenas, the Senate can by majority vote overrule the chief justice. But will McConnell really require his Senate colleagues to take the controversial vote to prevent witnesses from appearing in the Senate trial? Every Republican senator who votes to bar witnesses from testifying, overruling a Republican-nominated Supreme Court justice, will be seen as complicit in the White House’s stonewalling of the impeachment inquiry. (Those standing for re-election in 2020 in purple states should be wary of earning that stigma.)

Few senators likely know what Bolton or Mulvaney may say in depositions or in testimony. But once their testimony is committed under oath, the House managers in charge of presenting the case for impeachment will have a road map for questioning them in the Senate trial.

And, while the Senate has latitude to change the impeachment trial procedures by a majority vote, no particular legal justification exists for deviating from what governed the last presidential impeachment.

Still, Republicans want to close their ears to this evidence. Sen. Mike Braun, R-Ind., laid out the Republican theme opposing live testimony, saying, "We’ve heard everything up to this point three times.”

At least one of his Republican colleagues, though, Sen. Lindsey Graham, R-S.C., has famously said that he is refusing to even read the testimony of witnesses in the House impeachment inquiry. So only by sitting in his seat in the Senate will Graham (and possibly others) hear any evidence supporting the impeachment articles.

And maybe, just maybe, John Henry Wigmore’s assertion in “Evidence,” oft-cited by the Supreme Court, that “cross-examination is the greatest legal engine ever invented for the discovery of truth“ will result in new and damaging disclosures of evidence about Trump’s involvement in the Ukraine scheme that will trump the political considerations that seem to, at this stage, all but assure the president’s eventual acquittal.

At a minimum, the American public will learn of the depths of the involvement by administration officials in withholding congressionally-authorized military aid to Ukraine to fight Russian military aggression.

And, unlike the vociferous defense of Trump by House Republicans during committee hearings, no senator can rail against Trump’s impeachment during the trial because senators may not speak during the actual impeachment trial. They are jurors, not advocates, once the trial begins. While a senator can submit a question in writing to be asked of a witness, the chief justice will decide whether the question is proper and the senator is barred from defending his or her question. (“It shall not be in order for any Senator to engage in colloquy,” according to the rules.)

Any defense, then, will have to be mounted by Trump’s lawyers, who will be at a serious disadvantage because the president rejected the House Judiciary Committee’s invitation to participate in its impeachment hearing. Thus, his lawyers will not be as familiar with the witnesses and documentary evidence as the House managers already are — and they will have only until early January to get ready.

In “Federalist 62,” Alexander Hamilton justified the Constitution’s choice of the Senate to be the jury in an impeachment trial as the body able to “preserve, unawed and uninfluenced, the necessary impartiality between the individual accused and the representatives of the people, his accuser.”

Republican efforts to abandon impartiality and block a full airing of the facts would profoundly dismay the framers of the Constitution who had placed their faith in a future Senate that would do its duty faithfully.