We’ve become so inured to Donald Trump’s proto-fascism that we barely blink an eye when we learn that he tried to manipulate the 2020 election. Yet the most recent revelation should frighten every American to their core.

On Friday, the House oversight committee released notes of a 27 December telephone call from Trump to then acting attorney general Jeffrey Rosen, in which Trump told Rosen: “Just say the election was corrupt + leave the rest to me and the R congressmen.” The notes were taken by Richard Donoghue, Rosen’s deputy, who was also on the call.

The release of these notes has barely made a stir. The weekend news was filled with more immediate things – infrastructure! The Delta strain! Inflation! Wildfires! In light of everything else going on, Trump’s bizarre efforts in the last weeks of his presidency seem wearily irrelevant. Didn’t we already know how desperate he was?

In a word, no. This revelation is hugely important.

Rosen obviously rejected Trump’s request. But what if Rosen had obeyed Trump and said to the American public that the election was corrupt – and then “left the rest” to Trump and the Republican congressmen? What would Trump’s and the Republicans’ next moves have been? And which Republican congressmen were in cahoots with Trump in this attempted coup d’état?

Make no mistake: this was an attempted coup.

Trump knew it. Just weeks earlier, then attorney general William Barr said the justice department had found no evidence of widespread fraud that could have overturned the results.

And a few days after Trump’s call to Rosen – on 2 January – Trump told Brad Raffensperger, Georgia’s secretary of state, to “find” votes to change the election outcome. He berated Raffensperger for not doing more to overturn the election.

Emails released last month also show that Trump and his allies in the last weeks of his presidency pressured the justice department to investigate totally unsubstantiated claims of widespread election fraud – forwarding them conspiracy theories and even a draft legal brief they hoped would be filed with the supreme court.

Some people, especially Republican officeholders, believe we should simply forget these sordid details. We must not.

For the first time in the history of the United States we did not have a peaceful transition of power. For the first time in American history, a president refused – still refuses – to concede, and continues to claim, with no basis in fact, that the election was “stolen” from him. For the first time in history, a president actively plotted a coup.

It would have been bad enough were Trump a mere crackpot acting on his own pathetic stage – a would-be dictator who accidentally became president and then, when he lost re-election, went bonkers – after which he was swept into the dustbin of history.

We might then merely regret this temporary lapse in American presidential history. At best, Trump would be seen as a fool and the whole affair an embarrassment to the country.

But Trump was no accident and he’s not in any dustbin. He has turned one of America’s two major parties into his own cult. He has cast the major political division in the US as a clash between those who believe him about the 2020 election and those who do not. He has emboldened state Republicans to execute the most brazen attack on voting rights since Jim Crow. Most Republican senators and representatives dare not cross him. Some of his followers continue to threaten violence against the government. By all accounts, he is running for president again in 2024.

Donald Trump’s proto-fascism poses the largest internal threat to American democracy since the civil war.

What to do about it? Fight it, and the sooner the better.

This final revelation – Trump’s 27 December call to the acting attorney general in which he pleads “Just say the election was corrupt + leave the rest to me” – should trigger section 3 of the 14th amendment, which bars anyone from holding office who “engaged in insurrection” against the US. The current attorney general of the United States, Merrick Garland, should issue an advisory opinion clearly stating this. If Trump wants to take it to the supreme court, fine.

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California at Berkeley and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a columnist for The Guardian US