The most emotionally and politically potent moment of last week’s Democratic National Convention came on its final night, when Khizr Khan held up a pocket-sized copy of the US Constitution and spoke directly to the Republican Party’s 2016 presidential nominee.

“Donald Trump,” he said, “you’re asking Americans to trust you with their future. Let me ask you, have you even read the United States Constitution?”

Cheered on by the delegates, and by a nation that has been waiting for just this rebuke of Trump and Trumpism, the Muslim father of a US Army captain who was killed in a Baghdad suicide bombing 12 years ago announced: “I will gladly lend you my copy.”

As Democrats campaign in the weeks and months following the convention that nominated Hillary Clinton for the presidency and Tim Kaine for the vice presidency, they should endeavor to lend a copy of the Constitution to America.

The race against Donald Trump and the remnant of the Republican Party that has embraced him does not need to get bogged down by the tiresome repetition of Trump’s offenses against common sense and common decency. They are too many to catalogue, and the list grows too rapidly to keep up.

The response to Trump needs to go to the heart of the matter, as Khizr Khan did.

Trump may or may not have read the United States Constitution. (The candidate claims, with a pathetic defensiveness that illustrates just how deeply this charge stings, that “Mr. Khan who has never met me, has no right to stand in front of millions of people and claim I have never read the Constitution, (which is false) and say many other inaccurate things.”)

But the Republican nominee surely has not understood or respected the founding document.

Trump refuses to recognize the constitutional commitment that Mr. Khan (a Harvard-educated legal scholar who has worked for many years as a legal consultant) highlighted: “equal protection” under law.

The American Civil Liberties Union has produced an analysis of the Republican candidate’s public statements and policy positions that details the extent to which Trump would shred the Constitution in general and the Bill of Rights in particular.

It is a sobering assessment that ought not be left on the sidelines of this campaign.

“Taken together, his policies and positions, if put into place, would violate the Constitution and federal and international law,” says Anthony Romero, the executive director of the ACLU, which determined that “Trump’s proposals would violate the First, Fourth, Fifth, and Eighth Amendments of the Constitution.”

Trump’s most severe and threatening disrespect for the Constitution involves his absolute disregard for its most basic premise: that all Americans must be afforded equal protection under the law—no matter what their faith, class, race, ethnicity, national origin, gender, sexuality, age, or physical capability.

To their credit, organizers of this year’s Democratic National Convention embraced and celebrated diversity.

They also highlighted the threat that Donald Trump poses to diverse peoples.

Now they should close the circle by highlighting an understanding of the Constitution as a document that was written and amended with the purpose of providing protection against the threats posed by authoritarians who disregard America’s history and America’s promise.

Republicans have tried to claim the Constitution as their own in this election cycle. They imagine that a country founded by believers in a “wall of separation between church and state” would have favored governance based on the dictates of a particular religion. Their platform is theocratic in its language and spirit, employing arguments never before considered by a major American political party. It’s extremism is such that People for the American Way’s “Right-Wing Watch” team has observed, “Four years ago, we called the GOP platform ‘a far-right fever dream, a compilation of pouting, posturing, and policies to meet just about every demand from the overlapping Religious Right, Tea Party, corporate, and neo-conservative wings of the GOP.’ Yet this year’s platform is even further to the right.”

It is not just the party’s proposed deconstruction of the wall of separation between church and state that should concern thinking Americans, however.

The whole of Trump’s disregard for the Constitution should be a central theme of the campaign that Democrats mount this fall.

Republican strategists are smart. They know that Americans have high regard for their Constitution, that they see it as a set of ideals and as a source of protection. And Republicans have made much of their claim that they are “constitutional conservatives” doing battle to defend the document.

Now, however, the Republican Party has nominated for the presidency an authoritarian who disregards simple constitutional concepts: including those that bar religious tests and targeted assaults of the rights of religious, racial, and ethnic minorities.

Trump’s despotic language knows no end. On the day after the Democratic convention, when his supporters in Colorado Springs erupted in Clinton-attacking chants of “lock her up,” the candidate replied, “I’ve been saying let’s just beat her on November 8th. But you know what, I’m starting to agree with you.”

That’s not the language of a defender of the United States Constitution—be she a “constitutional conservative” or a champion of Tom Paine’s radical preachments. That is the language of an authoritarian who is grasping for power. And that authoritarian proposes to use that power to assault not just his opponents but the Constitution.

If by some chance Trump becomes president, patriots of all persuasions and ideologies should celebrate the fact that Anthony Romero and the American Civil Liberties Union say “We stand ready to defend our Constitution.”

But it ought not come to that.

Democrats would be wise to adopt Romero’s promise and adopt as a fall campaign pledge the promise: “We stand ready to defend our Constitution.”

The threat that Trump poses is self-evident. The response that Democrats mount as a counter to that threat should be equally self-evident.

This is smart politics—as a campaign for the Constitution and against authoritarianism will appeal not just to Democrats but to independents and responsible Republicans.

This is also necessary politics.

The 2016 general election campaign can and should be a referendum on the Constitution.

This is a “Which Side Are You On?” moment.

The questions that arise go beyond candidates and parties:

Will Americans defend the United States Constitution? Or will we allow an authoritarian and his minions to shred it?

Democrats should not be afraid to frame the political competition of this fall in such terms.

A failure to so frame it would fail not just their party but their nation.