President Obama during his speech Wednesday night at the 2016 Democratic National Convention, in Philadelphia. Photograph by Philip Montgomery for The New Yorker

It was about 8:40 P.M. last night when President Obama climbed aboard Air Force One for the hop to Philadelphia, where he was scheduled to speak at about 10:30 P.M. As an accomplished speaker, he must have known that the speech that would be fed into the teleprompters at the Wells Fargo Center was one of his best. As an astute politician, he must have known that, in other respects, too, the ground was being laid for a memorable night.

For the first two days of the Democratic National Convention, the leaks of hacked Party committee e-mails and the presence of large numbers of hardcore Bernie Sanders supporters had blurred the message that the Clinton campaign wanted to get out: Hillary Clinton is fit and ready to serve as Obama’s successor; Donald Trump isn’t. But by the time the wheels lifted at Joint Base Andrews, Trump’s earlier remarks encouraging Russia to spy on Clinton had been making news for almost twelve hours, and a number of Convention speakers had done yeoman work for the Democrats’ cause.

After Bill Clinton’s effort on Tuesday to humanize his wife, and to persuade Americans that a funny, well-meaning, and loving woman resides beneath her sometimes flinty exterior, the emphasis Wednesday was on building up her credentials as a Commander-in-Chief in dangerous times. Martin O’Malley, the former governor of Maryland, who criticized Clinton on various issues during his own ill-fated Presidential bid, got things going early on by declaring, “I have worked alongside her, and I have competed against her. And I’m here to tell you that Hillary Clinton is as tough as they come. She will stand up to ISIS. She will stand up to the Russians.”

In a compelling moment, Gabrielle Giffords, the former congresswoman from Arizona, who in 2011 suffered a serious brain injury during an assassination attempt, walked slowly onto the stage and said, “In Congress, I learned a powerful lesson: strong women get things done. . . . That’s why I am voting for Clinton.” John Hutson, a retired Navy rear admiral, demolished Trump’s claim to be the law-and-order candidate by pointing out his intention to violate an assortment of laws, and brought up Trump’s derogatory comments about Senator John McCain’s military record, saying, “Donald, you’re not fit to polish John McCain’s boots.”

While the President was still en route, Leon Panetta, the Californian who served under Obama as C.I.A. director and Secretary of Defense, brought up Trump’s comments earlier in the day, saying that the G.O.P. nominee “once again took Russia’s side.” Ignoring jeers from some Sanders delegates who chanted “No more war,” Panetta reminded the television audience that he had worked for nine Presidents and said, “I can tell you this: that in this election, there is only one candidate for President who has the experience, the temperament, and the judgment to be Commander-in-Chief, and that’s Hillary Clinton. . . . She is smart. She is principled. She is tough, and she is ready.” Vice-President Joe Biden and Senator Tim Kaine, who earlier in the evening was officially nominated as Clinton’s running mate, both kept up the assault on Trump and vouched for Clinton, while Michael Bloomberg, the former Mayor of New York, described himself as an independent but joined the Democratic chorus, saying, “The richest thing about Donald Trump is his hypocrisy.”

Obama took the stage at just before eleven. (The show was running late.) Although his remarks were to be a demolition job on Trump, and a testimonial to Clinton, they weren’t to be cast in the everyday language of campaign speeches. Obama and his speechwriters, as is their wont, had aimed higher than that. And they succeeded.

The speech didn’t immediately get to Clinton and Trump. Instead, Obama began with himself, returning to the D.N.C. in 2004, when he delivered the speech that made his career. “I was so young that first time, in Boston,” Obama recalled, with a wry smile. “Maybe a little nervous addressing such a big crowd. But I was filled with faith: faith in America, the generous, bighearted, hopeful country that made my story—indeed, all of our stories—possible.” He went on, “I stand before you again tonight, after almost two terms as your President, to tell you I am even more optimistic about the future of America.”

Since Ronald Reagan, almost all Presidents have said that they believe America’s best days lie ahead. Like Reagan, Obama has the capacity to make this sort of language sound like something more than a soundbite, and, although he hadn’t yet mentioned Trump’s name, it was immediately clear where, on this occasion, he was heading with it: to Cleveland, and Trump’s dismal, dystopian speech accepting the Republican Presidential nomination. After a fairly rote recitation of his Administration’s achievements in domestic and foreign policy, Obama said, “Fair to say, this is not your typical election. It’s not just a choice between parties or policies, the usual debates between left and right. This is a more fundamental choice—about who we are as a people, and whether we stay true to this great American experiment in self-government.”

What came out of Cleveland “wasn’t particularly Republican—and it sure wasn’t conservative,” Obama continued. Rather, it was “a deeply pessimistic vision of a country where we turn against each other, and turn away from the rest of the world. There were no serious solutions to pressing problems—just the fanning of resentment, and blame, and anger, and hate. And that is not the America I know.”

That America, Obama said, was “full of courage, and optimism, and ingenuity.” It was “decent and generous”—a place where people are “working hard and starting businesses . . . engineers inventing stuff, and doctors coming up with new cures . . . a younger generation full of energy and new ideas, not constrained by what is, ready to seize what ought to be.” And, “most of all,” a place where Americans of every creed, ethnicity, and sexual orientation are “all pledging allegiance, under the same proud flag, to this big, bold country that we love.”

As yet, Obama hadn’t mentioned Trump’s name, but he was making the case that the Republican nominee, a man who wraps himself in the flag and gins up nativist sentiment at every opportunity, wasn’t merely unfit for the Oval Office, he was un-American: the very charge that Trump has lobbed at the country’s first African-American President (without, perhaps, saying it outright). “That’s the America I know,” Obama went on. “And there is only one candidate in this race who believes in that future, and has devoted her life to that future . . . the next President of the United States, Hillary Clinton.”

The President now turned to the other business of the evening: building up the candidate whom he has endorsed. He recalled how “tough” an opponent she had been in 2008, saying, “For four years, I had a front-row seat to her intelligence, her judgment, and her discipline.” He praised her record in helping children and the families of fallen members of the armed services, and he recalled, not for the first time, her role arguing in favor of the mission that killed Osama bin Laden. Elaborating on something he said when he endorsed her last month, he said, “There has never been a man or a woman—not me, not Bill, nobody—more qualified than Hillary Clinton to serve as President of the United States of America.”