Biden wanted his Democratic convention speech to be a launchpad. It became his swan song.

Bittersweet.

The cheers for President Joe Biden as he stepped on stage at the Democratic National Convention Monday night were so deafening that they rattled the rafters at the United Center in Chicago − thanking him for a half-century in politics, a crucial victory in 2020 and nearly four hard-fought years in the White House since then.

And thanking him for now being willing to leave.

He looked nearly overcome by emotion as he embraced his daughter Ashley, who had introduced him to the crowd, pulling a handkerchief from his pocket to wipe his eyes.

The final speech on the convention's first night capped the most astounding turnaround in an election that has had more than its share of upheavals, including on the Republican side the unprecedented conviction of a former president on criminal charges and his defiant response to an assassination attempt.

Through all that, Donald Trump remains on the ballot, while Biden − a sitting president who had won every state primary and commanded the allegiance of almost every delegate at the convention − bowed to pressure from longtime allies who believed he could not win in November.

The triumphant acceptance speech he had been poised to deliver until just four weeks ago instead became his swan song.

"It's been the honor of my life to serve you as your president," Biden said. "I love my job. But I love my country more."

He didn't make any more of an explanation of why he was there to make a valedictory address rather than an acceptance speech.

He didn't need to explain it to this audience. "We love Joe!" they chanted.

The affection for Biden in the hall was sincere, but there wasn't a sense of regret. There was a sense of relief.

An election transformed

There were a few reminders of the signs of aging that had cost Biden, at 81 the oldest president in history, his political future. His voice was strong but his words sometimes slurred, and his gait was stiff.

This had to sting: The presidential race had been transformed, and Democratic optimism revived, the instant he stepped back from it.

Contributions from big donors and small ones surged. Polls in swing states improved. Trump, who left the Republican National Convention last month ready to choose his cabinet, suddenly seemed uncertain how to attack his new opponent.

Indeed, it is Trump, not Democratic resisters, complaining that Biden was the victim of an anti-democratic coup.

"We have him on the run now," Hillary Clinton said of Trump, addressing the convention an hour before Biden, now a fellow former nominee for the Democrats. She didn't have to mention that was a change.

Four years ago, the COVID-19 pandemic had denied Biden the opportunity to deliver the classic convention acceptance address, one engulfed in enthusiasm and optimism. Instead, he spoke to a camera in a dark and nearly empty room, a speech that lasted just 25 minutes and was at times somber in tone, befitting the moment.

This time, Biden came across as he often does — not as a grand orator, because he isn't one, but as decent and earnest, and basking in the enthusiastic response he was receiving.

In his speech, Biden described the daunting problems that loomed when he moved into the White House, as the pandemic was still raging and two weeks after the Capitol had been attacked by rioters trying to overturn the results of the election.

"A winter of peril and possibility," he called it, with challenges that had now been met. "Now, it's summer; the winter is passed."

He expounded on a litany of major legislation he had signed and historic actions he had taken, from negotiating a huge infrastructure bill to enacting gun laws to appointing the first Black woman to the Supreme Court to negotiating lower prices on drugs for seniors.

He denounced Trump as dangerous to democracy and unworthy of the presidency.

This is how Biden had planned to use his convention speech, as a launching pad to make the case that the first term had scored important achievements he could build on in a second. As it turned out, though, he then had to pivot to endorse Harris to run instead.

He called his choice of her in 2020 as a running mate "the best decision I ever made" and predicted, "She will be an historic president who puts her stamp on America's future."

Five more months in the Oval Office

To be sure, Biden remains president for another five months, the commander in chief and keeper of the nuclear codes. He vowed in his speech to do all he can in the time he has left in office.

"I've got a lot to do," he said. "I intend to get it done."

But the cold reality is that no legislation of controversy is likely to be enacted until the next president and the new Congress are sworn in next January. The focus of the political world already has shifted from the White House to the Naval Observatory, where the vice president resides, and to Mar-a-Lago, where Trump lives.

History takes time to make its judgment, and assessments of presidencies change for better and worse.

At the moment, Biden stands as a clearly consequential president for navigating the pandemic, helping steer the economy to a "soft landing," forging a united Western response to the Russian invasion of Ukraine, making the biggest investment in climate in history.

But a presidency bracketed by two Trump terms couldn't be seen as setting the country on a new course; it presumably would appear more like an aberration. And a reelected Donald Trump has vowed to dismantle the Biden agenda.

Much of Biden's legacy banks on denying Trump another term. That now depends on Harris.

"Join me in promising your whole heart to this effort," he said near the close of his speech. "That's where my heart will be. I promise I'll be the best volunteer the Harris-Walz campaign has ever seen."

First lady Jill Biden came on stage first when her husband's speech ended. Then Harris and second gentlemen Doug Emhoff walked on to embrace the Bidens, to bigger cheers.

This article originally appeared on USA TODAY: Biden wanted his Democratic convention speech to be a launchpad. It became his swan song.