The damage inflicted on the nation during Donald J. Trump’s first term in office pales in comparison to what he will do if he is elected to a second term. How can we know this? The best evidence is Trump himself. He has repeatedly demonstrated his willingness to tear the country apart.

“Donald Trump and his MAGA supporters,” Sean Wilentz, a historian at Princeton, writes in a forthcoming article in Liberties,

have made it clear that they will not accept defeat in November any more than they did when Trump lost four years ago. They believe that Trump is the one true legitimate president, that those who refuse to accept this fundamental fact are the true deniers, and that any result other than Trump’s restoration would be a thwarting of history’s purpose and a diabolical act of treason.

The authoritarian imperative has moved beyond Trumpian narcissism and the cultish MAGA fringe to become an article of faith from top to bottom inside the utterly transformed Republican Party, which Trump totally commands.

Like Wilentz, Laurence Tribe, a law professor at Harvard, does not mince words, writing by email:

All the dangers foreign and domestic posed by Trump’s cruelly vindictive, self-aggrandizing, morally unconstrained, reality-defying character — as evidenced in his first presidential term and in his unprecedented refusal to accept his 2020 electoral loss — would be magnified many times over in any subsequent term by three factors.

First, he has systematically eroded the norms and the institutional guardrails that initially set boundaries on the damage he and his now more carefully chosen loyalist enablers are poised to do in carrying out the dangerous project to which they are jointly committed.

Second, their failures to insulate themselves from electoral and legal constraints during the dry run of 2017-21 have led them to formulate far more sophisticated and less vulnerable plans for their second attempt at consolidating permanent control of the apparatus of our fragile republic.

And third, their capture of the Supreme Court and indeed much of the federal judiciary has put in place devastating precedents like the immunity ruling of July 1 that will license a virtually limitless autocratic power — if, but only if, they are not stopped during the epic struggle that will reach one climax this Nov. 5 and another next Jan. 6.

The most important reason a second Trump term would be far more dangerous than his first is that if he does win this year, Trump will have triumphed with the electorate’s full knowledge that he has been criminally charged with 88 felonies and convicted of 34 of them (so far); that he has promised to “appoint a real special prosecutor to go after the most corrupt president in the history of the United States of America, Joe Biden, and the entire Biden crime family”; that he intends to “totally obliterate the deep state” by gutting civil service protections for the 50,000 most important jobs in the federal work force, a central tenet of what he calls his “retribution” agenda.

Julie Wronski, a political scientist at the University of Mississippi, contended in an email that

The question is how much the Supreme Court presidential immunity decision will undermine institutional guardrails against Trump’s anti-democratic behavior. If there are no repercussions for his role in the Jan. 6 Capitol insurrection, intimidation of election officers, and casual handling of classified materials, then Trump will be emboldened to partake in such activities again.

Trump has made clear that norms of governance — e.g., civility, accepting electoral defeat, and treating members of the political opposition as legitimate holders of power — do not apply to him.

While Kamala Harris has pulled even with, if not ahead of, Trump in recent polling, Republican attacks on her have yet to reach full intensity, and the outcome remains very much up for grabs.

Bruce Cain, a Stanford political scientist, voiced concerns similar to Wronski’s by email:

Trump is more erratic, impulsive, and self-interested than your average candidate and is much bolder than most in testing the boundaries of what he can get away with. In political insider lingo, he is a guy who likes to put his toes right up the chalk line between legal and illegal activity.

There is some evidence that his bad traits are getting worse with old age, but the more serious problem is the lowering of institutional and political guardrails that constrained him in the past The decision in Trump v. the U.S. entitling a former president to “absolute immunity from criminal prosecution for actions within his conclusive and preclusive constitutional authority” and “presumptive immunity from prosecution for all his official acts” seems to me particularly problematic. The court left open the question of how to distinguish between official and unofficial acts. Trump’s personality is such that he will without doubt test the limits of this distinction.

Timothy Snyder, a historian at Yale and an expert on the regimes of Stalin and Hitler, wrote by email in reply to my inquiry: “It would be closer to the truth to think about a second Trump administration beginning from the images of Jan. 6, 2021. That is where Trump left us and that is where he would begin.”