President Biden took the stage on the first night of the Democratic National Convention for the last time as president — or as a candidate for the presidency — to cite the accomplishments of his single presidential term and the threat to democracy as the reasons Kamala Harris should succeed him as president.

“It’s been the honor of my lifetime to serve as your president,” Mr. Biden said in a speech that capped over five decades in office, as senator, vice president and president. “I love the job, but I love my country more. All this talk about how I’m angry at all those people (who) said I should step down — that’s not true. I love my country more, and we need to preserve our democracy in 2024.”

He received a thunderous standing ovation from the crowd and took a moment to wipe his eyes after his daughter, Ashley, introduced him. It took several minutes for the crowd to quiet, and his speech was interrupted at times by chants of, “We love Joe!” The party faithful filling the Chicago arena held up signs that said “We 💗 Joe.” 

Five months ago, Mr. Biden clinched the Democratic nomination and had every right to expect at that time he would be here tonight to take the mantle of Democratic nominee for the second time. Instead, he asked the crowd, “Are you ready to elect Kamala Harris and Tim Walz as president and vice president of the United States?” 

The president joked that he was too young to begin work in the Senate, elected at 29, and “too old” to remain as president. 

“I’ve made a lot of mistakes in my career, but I gave my best to you,” he said. 

In July, under increasing pressure to step aside as the nominee after a disastrous debate in June against former President Donald Trump, Mr. Biden acquiesced and announced he would give up the nomination and endorse Harris. 

The president reminisced Monday night about his decision to run for president after what he saw in Charlottesville in August 2017, when white supremacist rallies devolved into clashes that left one dead and several others injured. He also recalled the Jan. 6, 2021 assault on the Capitol, when rioters breached the Capitol and many tried to stop the certification of his election. 

“I believed then and I believe now that progress was and is possible,” Mr. Biden said. “Justice is achievable. And our best days are not behind us — they’re before us. Now, it’s summer. The winter has passed. And with a grateful heart, I stand before you now on this August night to report that democracy has prevailed. Democracy has delivered. And now, democracy must be preserved.” 

“You cannot say you love your country only when you win,” the president said, in a line that he has used about former President Donald Trump but now could apply to him, albeit for very different reasons. 

Everyone in the room, the president said, came together in 2020 to save democracy.

“As your president, I’ve been determined to keep America moving forward, not going back,” he said. “To stand against hate and violence in all its forms.”

Mr. Biden celebrated the accomplishments of his presidency, ticking off a list — 60 million new jobs, a record high stock market, bringing inflation down, the smallest racial wealth gap in 20 years and getting health insurance coverage for more Americans than ever.

When the crowd chanted, “Thank you, Joe,” at one point, Mr. Biden said, “Thank you Kamala, too!”

Mr. Biden then went after his former opponent, Donald Trump, and Trump’s promise of infrastructure week.

“And he never built a damn thing,” Mr. Biden said. 

“Donald Trump calls America a failing nation,” the president said, adding that Trump is wrong that America is failing. “He says we’re losing. He’s the loser, he’s dead wrong.” 

The president also noted violent crime has dropped across the country after spiking during the pandemic. 

“Crime will keep coming down when we put a prosecutor in the Oval Office instead of a convicted felon,” he said, nodding to Harris’ career as a prosecutor.

Mr. Biden said he’ll keep fighting for the freedom to vote and the freedom to love whomever one chooses.

“MAGA Republicans found out the power of women in 2022,” he said. “And Donald Trump is going to find out the power of women in 2024.” 

Turning to foreign concerns, the president said his team is “working around the clock” to secure a cease-fire deal in the Middle East and get aid to Palestinians in Gaza. Protesters criticizing Mr. Biden’s handling of the war stood outside the convention, at times slowing convention goers from entering. 

“Those protesters out in the street, they have a point,” he conceded. “A lot of innocent people are being killed on both sides.”

The president said Harris and Walz understand this nation must continue to be a place of possibilities, not just for the few, but for all, and Democrats need to ensure they win. 

“I promise I’ll be the best volunteer Harris and Walz’s campaign have ever seen,” the president said.