We have not seen much of Barack Obama lately, but on Friday he emerged to give a speech at the University of Illinois that was in part about the danger of authoritarianism in the White House — at the very moment that Donald Trump was descending into paroxysms of self-pity and giving free reign to his authoritarian impulses.

The most recent cause of Trump’s latest lurch downward is the op-ed by an anonymous Trump Administration official, saying that “many Trump appointees have vowed to do what we can to preserve our democratic institutions while thwarting Mr Trump’s more misguided impulses until he is out of office”.

Trump’s authoritarianism has been particularly conspicuous of late. On Friday, Trump actually demanded that his attorney-general launch an investigation to smoke out the disloyal reprobate behind the op-ed. On Thursday at a rally in Montana, Trump railed that the op-ed was “treason” — for the record, publishing a column criticising the President is nothing of the sort — and for good measure, Trump praised a local GOP candidate for having physically assaulted a journalist.

This comes only a few days after Trump took to Twitter to attack the Justice Department for bringing corruption charges against two Republican congressmen on the grounds that doing so threatened “two easy wins” for the GOP in the upcoming election.

Watching the contrast between Trump and Obama today, one could not help but be reminded of how the former president presented an idealistic — even arguably naïve — vision of America, one full of hopeful, hard-working, good-hearted citizens eager to come together to solve problems.

In his speech, Obama called for a “restoration of honesty and decency and lawfulness in our government” and insisted, in the face of the rage and polarisation coursing through politics, that “common ground exists. I have seen it. I have lived it”.

Whatever you thought of his policy choices, no one can say Obama didn’t regularly call Americans to be their best selves and of the country. We expect to hear that kind of unifying rhetoric from presidents of both parties. But one remarkable thing about Trump is that he never appeals to the better angels of our nature. He never asks Americans to be thoughtful, or generous, or kind, or empathetic, or considerate, or inclusive. Since Trump possesses none of those virtues, he cannot bring himself to demand them of others.

What he does instead is appeal to what is the worst in people, such as their fear and hatred and bigotry. This is the place where Trump truly has a touch of political genius: he can see into the dark depths of the American soul, find the ugliest things lying there and wrench them up to the surface.

And so, Obama tried to counter Trump with an unsurprising plea for us to reach for higher versions of ourselves. Yet there was a kind of odd combination of optimism and cold realism in the message he delivered. Specifically, he made the case that the only chance we have of reversing Trump’s authoritarian degradation of democracy is to get out and vote.

Obama’s riff on the need to vote this cycle is worth quoting at length:

“I am hopeful because out of this political darkness, I am seeing a great awakening of citizenship all across the country,” he said. “I cannot tell you how encouraged I’ve been by watching so many people getting involved for the first time, or the first time in a long time. They are marching and organising and registering people to vote, and they’re running for office themselves. Look at this crop of Democratic candidates running for Congress and running for governor and running for state legislature.”

Obama continued: “To all the young people who are here today, there are now more eligible voters in your generation than in any other, which means your generation now has more power than anybody to change things. “If you want it, you can make sure America gets out of its current funk. If you actually care about it, you have the power to make sure we seize a brighter future. But to exercise that clout, to exercise that power, you have to show up.

“In the last midterm elections in 2014, fewer than one in five young people voted. One in five. Not two in five, or three — one in five. Is it any wonder this Congress doesn’t reflect your values and your priorities? Are you surprised by that? This whole project of self-government only works if everybody’s doing their part. If you thought elections don’t matter, I hope these last two years have corrected that impression.”

A basic fact about our politics right now is that Trump has inspired a massive civic awakening, a large backlash among minorities, young people, and college-educated whites, particularly women, who are motivated by Trump’s multiple degradations of democracy and civic life — from the ugly, non-stop racist provocations, to the GOP-enabled self-dealing and corruption, to the authoritarian assaults on our institutions.

The undercurrent of realism here, one that Obama did not directly address but which was plainly on his mind, is that this civic awakening, that backlash, is about to collide with the GOP’s structural advantages in this election, which are rooted in geography and gerrymandering. The winner of this clash will determine whether the damage Trump is inflicting will continue in its present form or get much worse, or whether we will achieve something approaching real oversight and accountability that puts a check on it. In this sense, because Trump has elevated the threat to our democracy on so many fronts, these elections really do carry unusually high stakes for the future of our political system.

It is notable that Obama singled out down-ballot races as well because there’s another reason the stakes this time are so high. If Democrats can win back a fair amount of ground in the states, particularly by winning governorships in some of the big swing states — Democrats will have a hand in drawing the congressional maps for the next decade of redistricting. (In many states, governors can veto maps, forcing fairer ones.) This means these elections will go a long way towards determining whether Democrats can replace the maps that Republicans so effectively rigged in their favour — after they captured state legislatures all over the country in the 2010 elections — with far fairer ones.

In this sense, Obama’s reminder that the tendency of Democrats to sit out midterm elections has proven badly damaging to the party is particularly urgent right now. The 2010 bloodbath was one such election, and it put Democrats deep in a structural hole. Democrats now have a chance to begin to reverse the damage, both by winning the House to put a real check on Trump, and by gaining influence over redistricting, to unwind one of the GOP’s most pernicious structural advantages, one that, beyond its partisan implications, has only added to the degradation of our democracy.

But only if they vote.

• Greg Sargent and Paul Waldman write for The Plum Line, a reported opinion blog with a liberal slant — what you might call “opinionated reporting” from the Left