CHICAGO—This was supposed to be President Biden’s convention. Instead, this week he finds himself the opening night speaker at his party’s coronation of Vice President Harris.

Biden, 81, did something last month that few presidents before him have ever done. He stepped aside when he had one more race to run.

So Biden tonight will address the Democratic National Convention instead of closing it out on Thursday. He’s expected to give a speech where he argues former President Donald Trump is a danger to democracy, and ticks through the accomplishments of his administration.

But he’s going to be giving his vice president a lot of the credit, and urging voters to support her, instead of advocating for his own reelection bid.

“It’s not going to be a farewell speech, in my opinion,” said Ted Kaufman, Biden’s longtime friend. He said Biden will make the case that it is “really, really, really important that we elect a President Harris on Election Day.”

Biden’s brand was overcoming obstacles. But this one, he couldn’t beat

Biden’s decision last month was made all the more stunning because he is someone who has made a career of digging in and proving the doubters wrong.

Biden’s defiance was often his superpower during his decades-long career in politics.

But as withering criticism from his own party built day by day after his very bad debate against former President Donald Trump, that stubbornness became his Achilles’ heel.

To understand what made Biden believe he could hang on, you have to understand what else he’s survived.

“Joe Biden has been knocked down harder by life and gotten back up more, stronger, better than any … person I’ve known in my life,” said Sen. Chris Coons, D-Del., a close friend of Biden.

Biden overcame a series of challenges: the stutter he had as a child, the 1972 car accident that killed his wife and baby daughter, an aneurysm in 1988, the death of his son Beau from brain cancer in 2015, and more recently, the spiral of addiction and destruction that afflicted his son Hunter.

“He’s come back off the ground so many times whether it’s personally or politically,” said Barbara Boxer, who served with Biden in the Senate for years. “He doesn’t give up. He’s a deeply spiritual person.”

Boxer said Biden is driven knowing that he must still be here on this earth for a reason, to do everything he can “to make life better for everyone” that he can.

She worked with him on the Violence Against Women Act. Biden, then the chairman of the Senate Judiciary Committee, fought to get it added to the 1994 crime bill.

After years of work, Biden took a victory lap, saying he took “such pleasure” in knowing that he had overcome so much resistance to see the measure earn bipartisan support. To this day, Biden still cites it as one of the greatest accomplishments of his career.

While Biden’s time in the Senate taught him that tenacity could pay off, his multi-decade quest to become president confirmed it.

In 1987, he dropped out of his first race after his campaign failed to catch fire and then fell under the weight of a plagiarism scandal. “There will be other opportunities for me to campaign for president,” he said.

In 2008, as he dropped out his second failed attempt for the White House he shouted: “Let me make something clear to you — I ain’t going away.”

In 2008, Barack Obama made Biden his vice president. And in 2016, when Biden was expected to run again, his beloved son Beau died. By the time he emerged from the fog of grief, the Democratic establishment had lined up behind Hillary Clinton.

“Unfortunately, I believe we’re out of time,” Biden said at the time. “But while I will not be a candidate, I will not be silent.”

It seemed like the end of the road for Biden’s already long political career. Until it wasn’t. Outraged by then-President Trump’s response to the deadly white supremacist march in Charlottesville, Va., Biden made one more try.

“Everything that has made America, America — is at stake,” he said in his announcement.

Biden would become the oldest president in history. But for most of his primary race, it didn’t look like there was much chance of that happening.

“My colleagues here in the Senate were saying ‘Oh Joe, we love him, he’s a nice guy, he’s out of touch, he’s too centrist, he’s not a hashtag president.’ And he proved them wrong,” recalled Coons.

It was a recurring theme of Biden’s career in politics: counted out by almost everyone but himself.

In 2020, Biden was running well behind in a huge field of candidates, limping out of the early states. But then seemingly all at once, after a big win in the South Carolina primary, he rose up as the most electable choice. His younger opponents all dropped out, leaving Biden standing tall.

“Look I view myself as a bridge, not as anything else,” Biden said in March 2020. “There’s an entire generation of leaders you saw stand behind me. They are the future of this country.”

He defeated Trump. And in his very first press conference, Biden started getting questions about his political future.

“My plan is to run for reelection,” Biden said. “That’s my expectation.”

By the midterms in 2022, Biden’s approval rating was in the dumps, despite big legislative wins on infrastructure, gun safety and climate. He held one signing ceremony after another for bills that many people had written off as having little chance of passing.

But voters kept telling pollsters they wanted someone other than Biden to run. And so the questions kept coming. And Biden kept answering.

“My judgment of running when I announce, if I announce,” Biden said in a halting answer after the 2022 midterms. “My intention is that I run again, but I’m a big respecter of fate.”

He announced his run for reelection in April 2023, despite a swirl of questions about whether he was too old for another four years.

And then, on June 27, fate did intervene. Biden struggled to answer questions in the debate against Trump, sending Democrats into a tailspin.

Biden tried and failed to find his footing, and he was defiant as he had been so many times before.

“You’ve been wrong about everything so far. You were wrong about 2020. You were wrong about 2022 that we were going to get wiped out. Remember the red wave? You were wrong,” Biden told reporters on the tarmac after a rally in Wisconsin. “So, look, we’ll see.”

In the end, after resisting for weeks, Biden gave up the fight.

For Biden, there is no next campaign, there isn’t one more time. He is finally making good on that promise to be a bridge to the next generation, passing the torch to a historic pick — his vice president, Kamala Harris.

“Although it was a great honor being president I think I had an obligation to do the most important thing to do. We must — we must defeat Trump,” Biden explained in an interview with CBS News last week.

Harris seems has made history by becoming the first-ever Black and Asian American woman to be at the top of the ticket, and if she is able to beat Trump, Harris would break the highest and hardest glass ceiling in American politics. 

How Biden’s story is written in the history books, depends on whether his initial decision to run again and late decision to get out at the last minute leaves his party and its nominee enough time to get ready for November.

NPR’s Mallory Yu contributed to this report.