Four things happened on the last day of January 2020.

1. We crossed the Rubicon: The United States was envisioned as a republic. In a republic, the protection the people have against tyranny is our system of checks and balances. The judiciary checks the legislative branch when it passes unconstitutional laws. The executive has the power to veto congressional legislation, but the legislative branch can override that veto with a supermajority. When the president overreaches in a fundamentally dangerous way, Congress and the courts can check his or her will to power.

On Jan 31, 2020 (today), the Senate of the United States abdicated its constitutional responsibility to conduct a thorough trial after the House of Representatives sent a bill of impeachment against a sitting president. The president’s attorneys argued that what he did, if he did it, does not rise to the level of impeachment; that there is virtually no act that this president could commit that would deserve impeachment; that the president has essentially unlimited authority to behave in any way he wishes, including pressuring foreign governments to announce an investigation against his principal political rival.

In this situation, Congress was the people’s last guardrail against presidential excess, and the Senate decided to kick down that guardrail. In doing so, the U.S. Senate greatly diminished its constitutional authority. We now have what amounts to an elective monarchy in the United States. Tennessee’s Lamar Alexander at least had the honesty to acknowledge that what the president did was irresponsible, unacceptable and a violation of the trust we put in our chief executives. The Senate has now signaled to this president that if he uses other nefarious maneuvers to win re-election in November 2020, he will not be held responsible by the primary branch of the U.S. government, the Congress.

We have crossed a Rubicon. The tragedy is that tens of millions of American people either don’t know what just happened to the very foundation of our republic, or they don’t care because they are caught up in the cult of this darkly charismatic individual. Or perhaps just the Super Bowl.

It may sound overdramatic to say that Jan. 31, 2020, marked the death of the American republic, but as a scholar of Thomas Jefferson and the Constitution, I believe that is precisely what has happened. We will, of course, continue to be a rich and powerful nation. The Walmarts will continue to be full. The gas pumps will continue to deliver fuel. The Kardashians will continue to entertain us. But the republic, as republic, is now dead.

R.I.P. American Republic.

2. On the question of the impeachment trial alone, the allegation was that the president pressured a foreign government to announce an investigation of his chief rival, by withholding desperately needed military aid to a nation that has been invaded by Russia. The president’s attorneys argued countless times that no evidence links the president directly to the shakedown scheme.

When a material witness of unimpeachable integrity — an uncompromising lifelong Republican partisan and insider — came forward to announce that he had direct evidence of the president’s complicity based on actual and unambiguous conversations he had with that president, the Senate voted not to hear what he had to say under oath.

In what sense can this be called a thorough or fair trial when the U.S. Senate refused to listen to someone who could speak directly to the validity of the charges leveled at the president? It defies all logic, violates the fundamental principles of jurisprudence and ensures that no rational observer can ever conclude that the president has actually been exonerated. He has been protected by a slim majority in the Senate, but he has not been exonerated because the most material witness in the whole affair was not permitted to tell his story under oath.

When the history of this sad episode is written, there will always be a ring of illegitimacy and even Senate coverup in the Impeachment of Donald Trump. Put it another way: if the president is innocent, what does his administrative have to fear from a material eyewitness?

3. Trump supporters will celebrate his acquittal, but they are also unknowingly celebrating the death of constitutional restraint, due process, accountability, congressional oversight, checks and balances, the separation of powers doctrine and the guardrails and backstop of the U.S. Constitution. This story is no longer about Donald Trump, who will leave office at some point. But the damage done to the Constitution and the Idea of a Republic will outlast this and many future presidents, perhaps all of them.

Will it have been worth it to protect this one individual, this president who can serve no more than eight years at most, at the expense of the foundational principles of American life established in 1787 and preserved as inviolable for 233 years? The principal result of this impeachment episode is to render the Constitution’s impeachment clause a nullity, which means that future presidents will be able to violate their oaths with impunity.

4. The conclusion of the Trump impeachment drama is also the final death of Thomas Jefferson’s vision of America: that in a republic the people are sovereign; that the people guard their liberties, rights and prerogatives with stern vigilance; that they restrain and rebuke their president whenever he breaks faith with the people and exceeds his authority as outlined in Article II of the Constitution; that they err on the side of liberty rather than power.

Jefferson believed that the people of the United States would be sufficiently well-educated and well-informed to know what was at stake in the way their government acted and that they would vindicate his belief in their civic understanding in times of political and constitutional crisis. If in this situation the American people stepped back to analyze what it means for the U.S. Senate to curtail an impeachment trial before all the material facts were brought to light — particularly when the most material witness is denied his opportunity to clarify the very allegation at the heart of the impeachment —they would see that they have crossed a Rubicon, in this case an apparently invisible Rubicon, from which it will be exceedingly difficult to return to due process, checks and balances and constitutional order. In his famous Kentucky Resolutions (1798) Jefferson wrote, “In questions of power, then, let no more be said of confidence in man, but bind him down from mischief by the chains of the Constitution.” We have failed to bind President Trump “down from mischief by the chains of the Constitution.”

Jefferson thought we were up to it. If he could see what we have done, I believe he would say one of two things: either that Adams was right and we are not really up to the grave challenge of protecting our rights and liberties; or that we must double and then double again civics education, so that the people understand what a dangerous threshold we have now crossed, perhaps forever.

I repeat: This crisis is no longer about Donald Trump. Whatever you think about Trump is now immaterial because what has been on trial is the capacity of a republic to self-correct before it is too late. In a strange and ironic sense, Donald Trump is now the least of our worries.

When historians look back at the decline and fall of the American republic, Friday, Jan. 31, 2020, will now inevitably be one of the most significant, if not the most significant dates.

I know that what I have written here will be regarded by Trump’s partisans as an attack on the president they revere. That will only prove that they do not see what is actually at stake here.

The die has been cast.

For more from Clay Jenkinson, go to jeffersonhour.com.