That was before Trump resisted the peaceful transition of power, before a majority of House Republicans voted against certifying Biden's election, before a mob attacked Congress and before Democrats installed metal detectors on the House floor and feared their GOP colleagues might literally kill them.
Now, when Biden takes the inaugural stage on Wednesday that weeks earlier was overrun by rioters, the former backslapper of the Senate, who has bragged about his ability to work with even former segregationists, will be torn between his instincts for reconciliation and demands for accountability in order to prevent this dark chapter of American history from being swept under the rug.
"It's wonderful that he wants to unite the country, but he must be just as relentless in pursuing justice," said NBC News presidential historian Michael Beschloss. "In almost every presidential decision, there's a tension between unifying the country and dividing it, reconciliation and pursuing justice. But there are moments in history where this really flares up, and this is one of those moments."
In the wake of the Capitol assault, Republicans said dwelling on the past would only let the wound fester, with Florida Sen. Marco Rubio saying, "Biden has a historic opportunity to unify America" that would be squandered by impeaching Trump.
But Democrats see these pleas as hollow. They say letting anyone off the hook will only breed impunity and encourage future attacks on democracy.
"Without accountability, there cannot be unity," Rep. Chellie Pingree, D-Maine, said in a statement supporting a motion to investigate whether any GOP lawmakers violated their oath of office by engaging in insurrection.
The new Democratic administration will now face a host of questions about how to deal with the outgoing one.
Should Republican members of Congress be censured or expelled if they had any role in the riot? Should Trump be investigated and prosecuted for potential crimes? What about members of his administration who, say, participated in family separation at the border? Should Trump be welcomed as a member of the so-called ex-presidents club? Should he get the perks and office allowances bestowed on former chief executives?
Biden has pledged to be "a president for all Americans," but does that include people who question or undermine American democracy? What about the millions of Trump voters who don't think he was legitimately elected?
More immediately, a newly Democratic Senate will have to balance Trump's impeachment trial with Biden's legislative agenda.
"Hopefully, the trial will not be a lengthy trial," incoming White House chief of staff Ron Klain said Friday.
Biden will set the tone in his inaugural address Wednesday. He will face a mostly deserted National Mall, which has been closed for security reasons, filled with National Guard troops in fatigues and toting rifles instead of throngs of revelers.
"Except for Lincoln's second inaugural, and maybe FDR's later ones, it's hard to think of a president who is taking office when the idea of America has been tested more than over the last four years and the last four weeks," said David Litt, a former speechwriter in President Barack Obama's White House.
But Litt said Biden can speak directly to the American people, most of whom accept his election and were horrified by the riot, and draw on his experience and temperament to be a "calming influence."
"Simply by being presidential, Biden will summon our better angels," he said. "I think that will be unifying to Americans, whether or not Republican politicians will be able to admit it."
President Abraham Lincoln's second inaugural address, inscribed on his memorial, was an eloquent call to "bind up the nation's wounds" in the waning days of the Civil War, with "malice toward none" and "charity for all."
Some recent scholars, though, have wondered if Lincoln and successors were too quick to pardon and welcome back into the fold officials of the defeated Confederacy, reconciliatory moves that helped lay the groundwork for decades of brutal white supremacy under the Jim Crow era.
"Historically, America is not very good at looking back. We tend to press on without fully reckoning with the causes and consequences of our darker hours," said historian Jon Meacham, whose work Biden has publicly cited.
"This needs to change, and we have an opportunity to change it in our own time. There must be accountability for lies and lawbreaking. And we must learn from our mistakes. You cannot heal wounds you choose to ignore," Meacham added.
Sen. Bob Casey, D-Pa., a Biden ally from his hometown of Scranton, said Biden is uniquely well positioned to try to make real his inauguration theme of "America United."
"He'll work at it every day and try to make deals with Republicans where he can. He'll be patient," Casey said in an interview. "I think he'll be more patient than I would be, frankly, and I'm a very patient person. But it doesn't mean that he's going to keep extending his hand and letting them bite his hand every day."
Still, Biden surprised many observers by deciding not to nominate any Republicans to his Cabinet and by not encouraging Trump to attend next week's inauguration. He did welcome Vice President Mike Pence.
President Gerald Ford controversially pardoned his disgraced predecessor, President Richard Nixon, to avoid a "prolonged and divisive debate" about whether and how Nixon should be held accountable. And some, including former FBI Director James Comey, are now suggesting Biden consider doing the same for Trump "as part of healing the country."
Biden has already ruled out a pardon for Trump, saying at an MSNBC town hall before the election that he would defer entirely to prosecutors and not get involved. And the fact that Democrats are set to control Congress means the party's leaders in the Capitol will decide what to do with problematic GOP members, allowing Biden to transcend those immediate decisions.
But the new president will set the tone for how former Trump officials and defenders should be treated in public life.
Frank Sharry, who runs the liberal immigration reform group America's Voice, said any government officials involved in Trump's family separation policy, in which young children were removed from their parents and locked in detention facilities, "should be drummed out of public life and shunned by decent society for the rest of their lives."
That would be a break from precedent, however. Incoming presidents have largely avoided dredging up the sins of the predecessors.
Obama, for instance, decided against formally penalizing officials who helped carry out President George W. Bush's torture and warrantless wiretapping programs, saying, "We need to look forward as opposed to looking backwards."
Tom Perriello, a former Democratic congressman from Virginia, said he hoped Biden would learn from his experience as Obama's vice president.
"There's a learning curve. Obama put a lot of stake in bipartisanship. We joked in the first years that the only way to get a meeting with Obama was to be a Republican. And he got zero credit for it," Perriello said. "Obama wanted to be the Reagan of the Democratic Party and bring the country together — and he was capable of doing it — but the Republicans wouldn't let him."
Perriello, who has worked in foreign countries recovering from civil war and is now the executive director of the Open Society Foundations U.S., said his experience in places like Kosovo, Sierra Leone and Afghanistan have shown him that short-term unity can sow seeds for long-term problems.
"A lack of accountability is the quickest path to instability and future division," Perriello said. "Accountability can take a lot of forms, whether that's prosecution, a truth commission."
But it has to involve contrition, something he said a practicing Catholic like Biden would understand.
"The Catholic Church is very big on forgiveness — but you have to confess," he said.