After months of hyping conspiracy theories and pressuring election officials to falsify results, Donald Trump incited a mob to storm the U.S. Capitol and stop Congress from certifying the presidential election. If this does not warrant conviction in his upcoming Senate trial, what possibly could?

The Senate must convict Trump and disqualify him from ever holding office again.

First, Trump's actions easily qualify as an impeachable offense. The Senate may convict and disqualify Trump if he committed “treason, bribery, or other high crimes and misdemeanors” under the Constitution. The key question, then, is whether Trump committed a high crime.

Of course he did. Trump may not have known the mob would physically breach the capital. And he may not have wanted five people to die as a result. But he organized and incited his supporters to physically stop Congress from performing its constitutional duty. 

This is not just a crime; and it's not just a high crime. Trump’s acts violated the most essential constitutional principle in our democracy, that the peaceful transfer of power follows an election. This principle is, indeed, the basic necessity on which the rest of our democratic system rests. The alternative to the peaceful transfer of power – the usurpation of power by an incumbent against the will of the people – is the antithesis of democracy.

Second, the Senate may convict and disqualify Trump even though he left office. The text of the constitution doesn't limit Senate trials to incumbents. And there are numerous examples in both American and British law of officials being impeached after leaving office.

Of course, if the contrary were true – and a president could escape a Senate trial by resigning or committing crimes just before leaving office – then the constitution’s disqualification remedy would be hollow. And, ultimately, the Senate resolves open constitutional questions regarding its own proceedings.

Finally, Trump’s efforts to overturn the election conclusively establish he is unfit to be president. A presidential election is the ultimate source of legitimacy in our democracy. It is the only time all Americans come together and vote on the same question. This legitimacy weighed in Trump’s favor for years – protecting him against widespread efforts to remove him from office – even though his behavior was consistently disturbing. The people had spoken in 2016; and they had elected Donald Trump.

Yet this same essential consideration – that presidential elections are the deepest reflection of the people's will that our system affords – led to Trump’s catastrophic demise when he tried to reverse Joe Biden’s victory.

The constitution provides enormous leeway for presidential misbehavior. It is not an impeachable offense to be crass, inappropriate, immoral, irrational, even reckless. But the constitution likewise has foundational rules that presidents must follow. For months, Trump was at war with the most fundamental one of all, the peaceful transfer of power. And this culminated in his incitement of the mob that sought, through violence, to overturn the election.

Donald Trump’s behavior was an offense – a constitutional high crime – unlike any other in our nation's history. He must never hold office again.

William Cooper is an attorney who has written for The Wall Street Journal, New York Daily News, Baltimore Sun, Orlando Sentinel and USA Today, among others.