WILMINGTON, Del. — Joe Biden accept­ed the Demo­c­ra­t­ic pres­i­den­tial nom­i­na­tion with a vow to be a uni­fy­ing “ally of the light” who would move an Amer­i­ca in cri­sis past the chaos of Pres­i­dent Don­ald Trump’s tenure.

In his strongest remarks of the cam­paign, Biden spoke Thurs­day night both of return­ing the Unit­ed States to its tra­di­tion­al lead­er­ship role in the world and of the deeply per­son­al chal­lenges that shaped his life. Vir­tu­al­ly every sen­tence of his 22-minute speech was designed to present a sharp, yet hope­ful, con­trast with the Repub­li­can incumbent.

“Here and now I give you my word: If you entrust me with the pres­i­den­cy, I will draw on the best of us, not the worst. l’ll be an ally of the light, not the dark­ness,” Biden said. “Make no mis­take, unit­ed we can and will over­come this sea­son of dark­ness in America.”

For the 77-year-old Biden, the final night of the Demo­c­ra­t­ic Nation­al Con­ven­tion was bit­ter­sweet. He accept­ed a nom­i­na­tion that had elud­ed him for over three decades because of per­son­al tragedy, polit­i­cal stum­bles and rivals who proved more dynamic.

But the coro­n­avirus denied him the typ­i­cal cel­e­bra­tion, com­plete with the cus­tom­ary bal­loon drop that both par­ties often use to fete their new nom­i­nees. Instead, Biden spoke to a large­ly emp­ty are­na near his Delaware home.

After­ward, fire­works lit the sky out­side the are­na, where sup­port­ers wait­ed in a park­ing lot, honk­ing horns and flash­ing head­lights in a moment that final­ly lent a jovial feel to the event.

The keynote address was the speech of a life­time for Biden, who would be the old­est pres­i­dent ever elect­ed if he defeats Trump in Novem­ber. Trump, who is 74, pub­licly doubts Biden’s men­tal capac­i­ty and calls him “Slow Joe,” but with the nation ing, Biden was firm and clear.

Still, the con­ven­tion leaned on a younger gen­er­a­tion ear­li­er in the night to help ener­gize his sprawl­ing coalition.

Tam­my Duck­worth, an Illi­nois sen­a­tor who lost her legs in Iraq and is rais­ing two young chil­dren, said Biden has “com­mon decency.”

Cory Book­er, only the ninth African Amer­i­can sen­a­tor in U.S. his­to­ry, said Biden believes in the dig­ni­ty of all work­ing Americans.

And Pete Buttigieg, the 38-year-old for­mer South Bend, Indi­ana, may­or and a gay mil­i­tary vet­er­an, not­ed that Biden came out in favor of same-sex mar­riage as vice pres­i­dent even before Pres­i­dent Barack Obama.

“Joe Biden is right, this is a con­test for the soul of the nation. And to me that con­test is not between good Amer­i­cans and evil Amer­i­cans,” Buttigieg said. “It’s the strug­gle to call out what is good for every American.”

Above all, Biden focused on unit­ing the nation as Amer­i­cans grap­ple with the long and fear­ful health cri­sis, the relat­ed eco­nom­ic dev­as­ta­tion, a nation­al awak­en­ing on racial jus­tice — and Trump, who stirs heat­ed emo­tions from all sides.

Biden’s pos­i­tive focus Thurs­day night marked a break from the dire warn­ings offered by Oba­ma and oth­ers the night before. The 44th pres­i­dent of the Unit­ed States warned that Amer­i­can democ­ra­cy itself could fal­ter if Trump is reelect­ed, while Biden’s run­ning mate, Kamala Har­ris, the 55-year-old Cal­i­for­nia sen­a­tor and daugh­ter of Jamaican and Indi­an immi­grants, warned that Amer­i­cans’ lives and liveli­hoods were at risk.

Biden’s Demo­c­ra­t­ic Par­ty has sought this week to put for­ward a cohe­sive vision of val­ues and pol­i­cy pri­or­i­ties, high­light­ing efforts to com­bat cli­mate change, tight­en gun laws and embrace a humane immi­gra­tion pol­i­cy. They have drawn a sharp con­trast with Trump’s poli­cies and per­son­al­i­ty, por­tray­ing him as cru­el, self-cen­tered and woe­ful­ly unpre­pared to man­age vir­tu­al­ly any of the nation’s mount­ing crises and pol­i­cy challenges.

Vice Pres­i­dent Mike Pence, inter­viewed Fri­day on sev­er­al morn­ing talk shows, crit­i­cized Democ­rats as pre­sent­ing “a very grim pic­ture of the Unit­ed States” and said the Repub­li­can Nation­al Con­ven­tion next week will focus on what Trump has accom­plished, includ­ing on the econ­o­my and with his coro­n­avirus response.

Vot­ing was anoth­er prime focus of the con­ven­tion on Thurs­day as it has been all week. Democ­rats fear that the pan­dem­ic — and Trump admin­is­tra­tion changes at the U.S. Postal Ser­vice — may make it dif­fi­cult for vot­ers to cast bal­lots in per­son or by mail.

Come­di­an Sarah Coop­er, a favorite of many Democ­rats for her videos lip sync­ing Trump’s speech­es, put it blunt­ly: “Don­ald Trump doesn’t want any of us to vote because he knows he can’t win fair and square.”

Biden’s call for uni­ty comes as some strate­gists wor­ry that Democ­rats can­not retake the White House sim­ply by tear­ing Trump down, that Biden needs to give his sprawl­ing coali­tion some­thing to vote for. That’s eas­i­er said than done in a mod­ern Demo­c­ra­t­ic Par­ty made up of dis­parate fac­tions that span gen­er­a­tion, race and ideology.

Though he has been in the pub­lic spot­light for decades as a Delaware sen­a­tor, much of the elec­torate knows lit­tle about Biden’s back­ground before he began serv­ing as Obama’s vice pres­i­dent in 2008.

Thursday’s con­ven­tion served as a nation­al rein­tro­duc­tion of sorts that drew on some of the most painful moments of his life.

“I know how mean and cru­el and unfair life can be some­times,” Biden said. He added: “I found the best way through pain and loss and grief is to find purpose.”

As a school­boy, Biden was mocked by class­mates and a nun for a severe stut­ter. He became a wid­ow­er at just 30 after los­ing his wife and infant daugh­ter to a car acci­dent. And just five years ago, he buried his eldest son, who was strick­en by cancer.

From such hard­ship, Biden devel­oped a deep sense of empa­thy that has defined much of his polit­i­cal career. And through­out the con­ven­tion, Biden’s allies tes­ti­fied that such empa­thy, backed by decades of gov­ern­ing expe­ri­ence, makes him the per­fect can­di­date to guide the nation back from mount­ing health and eco­nom­ic crises.

His allies Thurs­day includ­ed Bray­den Har­ring­ton, a 13-year-old boy from Con­cord, New Hamp­shire. The boy said he and Biden were “mem­bers of the same club,” each with a stut­ter they’re work­ing to overcome.

He not­ed that Biden told him about a book of poems he liked to read aloud to prac­tice his speech and showed the boy how he marks his speech­es so they’re eas­i­er to read aloud.

“I’m just a reg­u­lar kid, and in a short amount of time, Joe Biden made me more con­fi­dent about a thing that’s both­ered me my whole life,” Har­ring­ton said.

The end of the care­ful­ly script­ed con­ven­tion now gives way to a far less-pre­dictable peri­od for Biden and his Demo­c­ra­t­ic Par­ty as the 2020 elec­tion sea­son speeds to its uncer­tain con­clu­sion. While Elec­tion Day isn’t until Nov. 3, ear­ly vot­ing gets under­way in sev­er­al bat­tle­ground states in just one month.

Biden has main­tained a polling advan­tage over Trump for much of the year, but it remains to be seen whether the Demo­c­ra­t­ic nominee’s approach to pol­i­tics and pol­i­cy will gen­uine­ly excite the coali­tion he’s court­ing in an era of uncom­pro­mis­ing partisanship.

Biden summed up his view of the cam­paign: “We choose a path of becom­ing angry, less hope­ful and more divid­ed, a path of shad­ow and sus­pi­cion, or we can choose a dif­fer­ent path and togeth­er take this chance to heal.”

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Peo­ples report­ed from New York.