Biden and his advisers have bet his candidacy on the idea that a focus on the incumbent, more than new policy ideas, anti-establishment crusades or ideological innovation, will win back the White House for Democrats.
The decision led to launching the campaign with a video about Trump's reaction to the 2017 Charlottesville protests, a circumstance the Biden team felt presented a clear contrast in values.
"The President of the United States assigned a moral equivalence between those spreading hate and those with the courage to stand against it," Biden said, referring to Trump's comment that "very fine people" were among the white nationalists and neo-Nazis at the violent conflict.
"And in that moment, I knew the threat to this nation was unlike any I had ever seen in my lifetime."
People familiar with Biden's thinking say that the Charlottesville, Virginia, protests and the President's reaction caused a real shift in 2017 in the former Vice-President's desire to run for president. Andrew Bates, a spokesman for the campaign, said Biden found the events "profoundly disturbing".
Two weeks later, Biden decided to break the tradition of former presidents and vice-presidents by writing an article that compared Trump to "the charlatans and the con-men and the false prophets who have long dotted our history".
"I think Charlottesville brought home to him in graphic terms what was at stake for the election in 2020," said Ted Kaufman, a longtime friend and adviser who worked on both of Biden's previous presidential campaigns. "When he is the most energised is with situations where some strong person is exerting power over someone weaker."
While re-election efforts are commonly referendums on the incumbent, a credo for other Democrats this year has been a rapt focus on either policy or personality - in both cases, their own, and not Trump's.
That flowed from Democratic congressional successes in the Midterm elections that hammered issues like healthcare and education and consigned the President to an afterthought.
As Biden planned a campaign launch, he and his aides decided they did not need to follow the traditional playbook of biographic details attached to a list of policy pronouncements, according to people familiar with the effort. Unlike most of his Democratic rivals, polls show he has nearly universal name recognition 46 years after he first became a federal officeholder.
The pending debate over the ideological direction of the Democratic Party was not an ideal starting place for a candidate aiming to keep the sheen of an heir apparent, his advisers counselled.
That was particularly true given that Biden's moderate and incremental instincts don't jibe with the ascendant and loudly liberal voices that have dominated the Democratic conversation so far.
The strongest place to begin was on the question of character, where they contend Biden has an advantage over the President in a head-to-head match-up.
"Even Mitch McConnell would probably tell you that," said one person familiar with the discussions, in reference to the Senate majority leader's long track record of cutting deals with Biden.
Biden's ability to control the story line of his campaign, however, is certain to be tested.
Before his announcement, he has been hit with questions about his past opposition to school busing and his friendships with former segregationist lawmakers, with whom he said he disagreed. His campaign announcement was disrupted by news that Anita Hill, the sexual harassment accuser of Justice Clarence Thomas, was still not satisfied with Biden's contrition for how he ran the confirmation hearing at which she appeared in 1991.
Biden's rival candidates also welcomed him to the race with criticism.
On his first day as a candidate, Biden attended a fundraiser at the home of a Comcast executive and former lobbyist in Philadelphia, prompting Senator Bernie Sanders to send an email to supporters noting that he was not spending time "at the home of a corporate lobbyist". Senator Elizabeth Warren told an audience in Iowa that during a fight over bankruptcy reform more than a decade ago, "Joe Biden was on the side of credit card companies".
Biden's confidants say they have no illusions about how hard the campaign will be, and Democratic strategists not on the campaign predict that Biden will have to pivot away from Trump and emphasise voter-pleasing policy positions to get through the primary.
"The central rationale for Joe Biden's candidacy is that Trump represents an existential threat to core values and that Biden is the best candidate to defeat Trump," said Geoff Garin, a Democratic pollster who is not working for his campaign.
"Biden still will need to lay out his progressive agenda for the next four years, presumably one that will focus on economics, especially creating jobs, rewarding work, and making it easier for people to get to and stay in the middle class."
The early signs are that Biden will also approach that task by referencing the better days. Rather than simply talk about the middle class, he spoke on The View about the need to "restore the dignity of work". His speech and rally at a union hall in Pittsburgh on Tuesday has been teased as a discussion about "rebuilding America's middle class."
The focus backward could exacerbate concerns about Biden's age, 76, which would make him the oldest president to ever take the oath of office. In recent months, he has been one of the only presidential contenders who has regularly appeared in public with note cards, including a paper he brought with him to his appearance on ABC.
In that interview, he initially struggled to answer a question about how his presidency would differ from President Barack Obama's Administration. He spoke about his close relationship with the former President and quiet disagreements, without offering specifics. But then he pivoted to the challenge ahead for his campaign.
"On a philosophic basis, it's about moving to the future," he said. "It's not about re-creating what we did. It's about taking the same decency and philosophy that we had and taking it into the future. There is so much we can do. My Lord."
Just what that will look like has not yet been described.
