Democratic National Committee via The New York Times / Former President Barack Obama addresses the Democratic National Convention via video on Wednesday in Philadelphia.

Former president Barack Obama chose the ground where our nation was born and our constitution written — the Museum of the American Revolution in Philadelphia — to warn 2020 voters that Donald Trump is a threat to our very democracy.

It was not a normal Obama speech. Not the kind we're accustomed to hearing.

To quote one New York Times pundit:

"It was Barack Obama quieter and louder than we had heard before. The audacity of hope was tempered by the veracity of the stakes."

Exhorting all Americans to find a way to vote for "my friend" Joe Biden and Kamala Harris, Obama was meticulous in his warning about why that vote is so necessary.

"Donald Trump hasn't grown into the job because he can't. And the consequences of that failure are severe: 170,000 Americans dead, millions of jobs gone while those at the top take in more than ever. Our worst impulses unleashed, our proud reputation around the world badly diminished and our democratic institutions threatened like never before."

And there was this:

"This president and those in power — those who benefit from keeping things the way they are — they are counting on your cynicism. They know they can't win you over with their policies. So they're hoping to make it as hard as possible for you to vote, and to convince you that your vote doesn't matter. That's how they win. That's how the economy will keep getting skewed to the wealthy and well-connected, how our health systems will let more people fall through the cracks.

"That's how a democracy withers, until it's no democracy at all."

But Obama's quiet yet thunderous words in an address during night three of the Democratic National Convention did something else. They made it possible for Kamala Harris, in her vice presidential nomination acceptance speech, to reintroduce herself to America not as a pushy prosecutor lambasting the incumbent president or his men, but as a daughter, sister, mother, wife, friend and thoughtful, caring person. It gave her a broad space to explain her own empathy and show why she will make such a good partner in governing with a future President Biden.

Harris accepted the nomination "committed to the values [her late mother] taught me" and to a "vision of our nation as a beloved community — where all are welcome, no matter what we look like, no matter where we come from or who we love. A country where we may not agree on every detail, but we are united by the fundamental belief that every human being is of infinite worth, deserving of compassion, dignity and respect. A country where we look out for one another, where we rise and fall as one, where we face our challenges and celebrate our triumphs — together."

Democrats have waited four years for Obama to speak out like this. After all, he carries the moral weight of two White House terms and enduring popularity with those revolted by Trump's abuses of power, divisive racial politics and constant stroking of his own ego.

But had Obama spoken out early and often, his rebuke of Trump would have been less singular in its stunning and explicit terms.

What's more, we suspect this was not a speech Obama ever thought he would give, wanted to give or would have to give.

He prefers, as he has shown us time and again, to talk of hope — that continuing audacity of hope.

And still, he summoned hope several times Wednesday night, especially in talking directly to young voters:

"You can give our democracy new meaning. You can take it to a better place. You're the missing ingredient — the ones who will decide whether or not America becomes the country that fully lives up to its creed. ... What we do echoes through the generations."

That's what made and will continue to make Obama's urgent warnings of "how a democracy withers" so deeply piercing.

"We can't let that happen. Do not let them take away your power. Don't let them take away your democracy," Obama said. "Make a plan right now for how you're going to get involved and vote. Do it as early as you can and tell your family and friends how they can vote, too. Do what Americans have done for over two centuries when faced with even tougher times than this — all those quiet heroes who found the courage to keep marching, keep pushing in the face of hardship and injustice.

"This administration has shown it will tear our democracy down if that's what it takes to win. So we have to get busy building it up — by pouring all our effort into these 76 days, and by voting like never before — for Joe and Kamala, and candidates up and down the ticket, so that we leave no doubt about what this country we love stands for — today and for all our days to come."

Heed the warning. Find the hope.