“You know me.” It’s one of Joseph R. Biden’s most-used lines, a folksy introduction, a deflection and a defense.Fact-check: It’s true. Mr. Biden has been around long enough to be on his third presidential run in four decades. Long enough to have had a dubious role in the 1991 Senate sexual harassment testimony of Anita Hill (for which he’s expressed regret), and then to be celebrated by the actress — Kerry Washington, the third-night host of his nominating convention — who played Ms. Hill in the 2016 HBO movie “Confirmation.”So the Democratic National Convention did not, like many conventions, have to introduce a new face to the audience. Instead, it built a connection.In clips, reminiscences and policy segments, it presented Mr. Biden as someone who has lived through troubles and consoled others in theirs: talking a colleague through grief; helping a young boy who, like Mr. Biden, struggles with a stutter.And Mr. Biden’s acceptance speech cast him as the Connecter-in-Chief.As you would expect of a challenger, he attacked President Trump’s handling of multiple national crises, including the pandemic that left him addressing a near-empty room. But he also, contrasting himself with a president who has said he hasn’t cried since he was a baby, offered not just to alleviate the country’s wrenching problems, but to feel them along with us.Mr. Biden’s speech was possibly the most ordinary thing about a shaky but fascinatingly experimental convention, forced to reinvent itself by the limits of Covid-19.Conventions have for decades been TV productions more than politically decisive or newsmaking events. But this was the first one that was purely TV: Stitched together from tapes and location shots, it had no existence in a physical space other than your screen.It also had a lot of audiences. It had to speak to the party’s moderates and its left. It spent a lot of time courting Trump-averse Republicans. And it had to reconcile a party with big constituencies of young people, women and people of color with its nominee, a 77-year-old white man.So the convention was a little bit like an old-time variety show for the Quibi age: A little something for everyone, and in quick, efficient bits. Speakers, live and taped, were brought on and hustled off. The keynote was sliced-and-diced among 17 speakers, sometimes trading off a phrase at a time. (Even Mr. Biden’s 24.5 minute speech, according to C-SPAN, was by far the shortest D.N.C. acceptance speech of the last four decades.)The whiplash was especially strong in Thursday’s first hour. Julia Louis-Dreyfus of HBO’s “Veep” delivered cutting jokes aimed at the sort of extremely online voter who would pick up a reference to Republicans mispronouncing Kamala Harris’s name, between earnest speeches and emotional stories. The historian Jon Meacham appeared, and so did the lip-syncing social-media Donald Trump impersonator Sarah Cooper — something for the PBS crowd, something for the TikTok kids.Senator Cory Booker and several of his primary opponents shared warm memories of running against Mr. Biden, in a round table Mr. Booker likened to a “Survivor” reunion special. The mogul and brief-lived Democratic candidate Michael Bloomberg spoke separately, having apparently blown the rest of his billions on flags.It was a lot — policy and personality, kitsch and cheek — but this convention had to reinvent the language of a political ritual that usually relies on thousands of party faithful, in person, as extras.How do you recreate the experience of hordes of roaring faithful when none of them can be there? You can’t. What you can do is find a way to create different but equally powerful emotions without them — as, for instance, Tuesday’s touchingly kooky delegate roll call travelogue did.Incendiary applause lines don’t work the same when no one is there to clap; zingers don’t land without someone to laugh. What does work is gravity and heart.And that, as Mr. Biden demonstrated in the convention’s climax, is something he can do.He stepped up to the podium from the shadows, prefiguring his first promise: “I will be an ally of the light and not the darkness.” This set up his larger theme, which was that, beyond policy, he saw the election as a moral struggle: between inclusion and division, decency and viciousness, caring and contempt.Mr. Biden had concrete criticisms and counterarguments to the president, especially on fighting the coronavirus: “It didn’t have to be this bad.”But it was when Mr. Biden talked about feeling the pandemic and its devastation that you could feel the speech take off.He asked to speak to those who had lost someone to Covid. He had lost too, he said — the convention had reminded us of this, and a four-night character arc paid off in this moment. “I know how mean, cruel and unfair life can be sometimes,” he said. “Your loved one may have left this Earth, but they’ll never leave your heart.”There have been over 170,000 Americans lost to the pandemic but no real public mourning. Mr. Biden didn’t say anything about the president who, visiting the site of a mass shooting last year, posed with an orphaned baby and gave a thumbs up. He didn’t say that the country might miss having a leader who believes that feeling loss doesn’t make you a loser. He didn’t need to.The camera pushed in closer. Mr. Biden, like his running mate, Kamala Harris, spoke from a podium in a near-empty hall, which gave Ms. Harris’s speech a haunting air on Wednesday. This time, the camera held him tight in the frame, matching his intimate speech. It wasn’t written as if it were meant to rouse a cheering crowd in the room. It was written to the camera, like a presidential address, and reached through the screen to the other side.The speech did end like Ms. Harris’s, with music anticlimactically playing in the desolate hall as Mr. Biden waved to supporters on a big screen — a substitution much pandemic-era TV has made for live audiences that will never stop feeling uncanny.But there was more. Mr. Biden masked up and went to the parking lot, where flesh-and-blood supporters, socially distanced by their wheels, were having a tailgate party. A modest spray of fireworks popped overhead in the dark.It wasn’t overwhelming. The backdrop wasn’t monumental. But it fit this American moment of tentative pleasures and small, improvised celebrations. Maybe there would be bigger fireworks someday, when there was more to cheer about. The important thing, for now, was the feeling.