Sitting in the Oval Office behind the famous Resolute desk in 2022, an animated US President Joe Biden described the challenge of leading a psychologically traumatised nation.

The United States and the world had endured a life-altering pandemic. There was a jarring burst of inflation and now global conflict with Russia invading Ukraine, as well as the persistent threat to democracy he felt Donald Trump posed.

How could Mr Biden possibly heal that collective trauma?

“Be confident,” he said emphatically in an interview with The Associated Press. “Be confident. Because I am confident.”

But in the ensuing two years, the confidence Mr Biden hoped to instil steadily waned. And when the 81-year-old Democratic president showed his age in a disastrous debate in June against Mr Trump, he lost the benefit of the doubt as well.

That triggered a series of events that led him on Sunday to step down as his party’s nominee for the November’s election.

Democrats, who had been united in their resolve to prevent another Trump term, suddenly fractured. And Republicans, beset by chaos in Congress and the former president’s criminal conviction, improbably coalesced in defiant unity.

Mr Biden never figured out how to inspire the world’s most powerful country to believe in itself, let alone in him.

He lost the confidence of supporters in the 90-minute debate with Mr Trump, even if pride initially prompted him to override the fears of politicians, party elders and donors who were nudging him to drop out.

Then Mr Trump survived an assassination attempt in Pennsylvania and pumped his fist in a show of strength. Mr Biden, while campaigning in Las Vegas, tested positive for Covid-19 on Wednesday and retreated to his Delaware beach home to recover.

The events over the course of three weeks led to an exit Mr Biden never wanted, but one that Democrats felt they needed to maximise their chance of winning in November’s elections.

Mr Biden seems to have badly misread the breadth of his support. While many Democrats had deep admiration for the president personally, they did not have the same affection for him politically.

Rice University historian Douglas Brinkley said Mr Biden arrived as a reprieve from a nation exhausted by Mr Trump and the pandemic.

“He was a perfect person for that moment,” said Mr Brinkley, noting Mr Biden proved in era of polarisation that bipartisan lawmaking was still possible.

Yet, there was never a “Joe Biden Democrat” like there was a “Reagan Republican”. He did not have adoring, movement-style followers as did Barack Obama or John F Kennedy. He was not a generational candidate like Bill Clinton.

The only barrier-breaking dimension to his election was the fact that he was the oldest person ever elected president.

His first run for the White House, in the 1988 cycle, ended with self-inflicted wounds stemming from plagiarism, and he did not make it to the first nominating contest.

In 2008, he dropped out after the Iowa caucuses, where he won less than 1% of the vote. In 2016, Mr Obama counselled his vice president not to run.

A Biden victory in 2020 seemed implausible, when he finished fourth in Iowa and fifth in New Hampshire before a dramatic rebound in South Carolina that propelled him to the nomination and the White House.

David Axelrod, a former senior adviser to Mr Obama who also worked closely with Mr Biden, said that history would treat Mr Biden kinder than voters had, not just because of his legislative achievements but because in 2020 he defeated Mr Trump.

“His legacy is significant beyond all his many accomplishments,” Mr Axelrod said. “He will always be the man who stepped up and defeated a president who placed himself above our democracy.”

But Mr Biden could not avoid his age. And when he showed frailty in his steps and his speech, there was no foundation of supporters that could stand by him to stop calls for him to step aside.

It was a humbling end to a half-century career in politics, yet hardly reflective of the full legacy of his time in the White House.

In March of 2021, Mr Biden launched 1.9 trillion dollars (£1.47 trillion) in pandemic aid, creating a series of new programmes that temporarily halved child poverty, halted evictions and contributed to the addition of 15.7 million jobs.

But inflation began to rise shortly thereafter as Mr Biden’s approval rating as measured by the AP-NORC Centre for Public Affairs Research fell from 61% to 39% as of June.

He followed up with a series of executive actions to unsnarl global supply chains and a trillion-dollar bipartisan infrastructure package that not only replaced aging infrastructure but improved internet access and prepared communities to withstand the damages from climate change.

In 2022, Mr Biden and his fellow Democrats followed up with two measures that reinvigorated the future of US manufacturing.

The CHIPS and Science Act provided 52 billion dollars (£40 billion) to build factories and create institutions to make computer chips domestically, ensuring that the US would have access to the most advanced semiconductors needed to power economic growth and maintain national security.

There was also the Inflation Reduction Act, which provided incentives to shift away from fossil fuels and enabled Medicare to negotiate drug prices.

Mr Biden also sought to compete more aggressively with China, rebuild alliances such as Nato and completed the US withdrawal from Afghanistan that resulted in the death of 13 US service members.

Russia’s invasion of Ukraine in early 2022 worsened inflation as Mr Trump and other Republicans questioned the value of military aid to the Ukrainians.

Hamas’s October 7 2023 attack in Israel sparked a war that showed divisions within the Democratic party about whether the United States should continue to support Israel as tens of thousands of Palestinians died in months of counterattacks.

The president was also criticised over illegal border crossings at the southern border with Mexico.

Yet it was the size of the stakes and the fear of a Biden loss that prevailed, resulting in a bet by Democrats that the tasks he began could best be completed by a younger generation.

“History will be kinder to him than voters were at the end,” Mr Axelrod said.