Joe Biden won the presidency because, at a moment when so many Americans were exhausted by the chaos and nastiness of the Trump era, he promised stability, decency and healing. At the heart of his candidacy was the vow to be “a president for all Americans” as he labored “to restore the soul of the nation.”

“The presidency itself is not a partisan institution,” Mr. Biden stressed the day after the election. “It’s the one office in this nation that represents everyone, and it demands a duty of care for all Americans. That is precisely what I will do.”

This is a soothing bit of uplift. But in a nation so starkly polarized, what does it even mean? While a record 81 million people voted for Mr. Biden, some 74 million voted to give President Trump four more years in office. Forget shared values: Americans cannot agree on a shared reality. Too many of us live in echo chambers, consuming information tailored to support our existing biases. Partisan warfare impels people to deny the legitimacy, even the humanity, of those with different viewpoints. What hope does any president have of bridging this gulf?

Mr. Biden might consider a three-pronged approach. Call it the Decency Agenda. The first element is turning down the heat of the culture wars as they intersect with politics. Too often, proxy fights create more outrage than progress.

The second part involves finding shared ground on policy that can push the country forward, even as it works to address its entrenched inequities and divisions. Could it at last be time for a serious “infrastructure week”?

The third element involves accountability. Not a truth commission mounted out of spite, or justice sought in the spirit of vengeance. But some way to get answers about what happened during the Trump administration, coupled with an attempt to restore some guardrails that proved insufficient to restrain Mr. Trump’s worst impulses.

In the coming weeks, we’ll have more to say about parts two and three of such an agenda.

It’s too simplistic to say that the way to tamp down America’s raging culture wars is for the incoming president to do the precise opposite of the departing one. But, in key respects, that prescription isn’t far-off. This is not so much about policy, although putting together an agenda with broad appeal and bipartisan support will be a big part of Mr. Biden’s challenge. This is about something more elemental — the president-elect’s conception of leadership.

Mr. Trump has approached the presidency, as he does everything, as a zero-sum proposition: To win, someone else must lose. Grounded in the politics of division, Trumpism is about attitude. The more antagonistic, the better. The president’s re-election campaign wanted to “make liberals cry again.”

This kind of leadership poisons the body politic, a little more each day. Presidents are role models. Their words and comportment influence their supporters and, more generally, set the tone for the national discourse. Mr. Trump has not merely normalized cruelty and boorishness; he has given it the imprimatur of the Oval Office.

One of Mr. Biden’s most basic jobs will be to model a different leadership — to reclaim what it means to be presidential in a way that restores dignity and humanity to the office. Some of what this requires is straightforward: Don’t demean political opponents or fellow world leaders. Don’t insult members of your own administration. Don’t accuse people who merely disagree with you of treason. Don’t have a Twitter tantrum every time your feelings get bruised. Or, maybe, stay off Twitter altogether.

More specifically, Mr. Biden will need to restore and reinforce some guardrails and norms that Mr. Trump tore down, in the recognition that not even presidents are above the law. He has already made his tax returns public, a welcome step back toward accountability. Going forward, he will need to make clear that key institutions — the Department of Justice, the intelligence community and the military, for starters — will be free from partisan meddling. His administration’s inspectors general must be treated as guardians, not turncoats, and they may need to be granted additional protections. He will need to acknowledge that oversight of the executive branch is a legitimate function of Congress, not something to be dismissed out of hand.

Speaking to the concerns of Mr. Trump’s supporters, without condemnation or condescension, will be crucial to Mr. Biden’s unification efforts. It helps that the new president has an unpolished, regular-guy appeal and a knack for connecting on a personal level that keeps him from seeming like a snooty elitist. His Catholic faith is important to him, which will resonate in many enclaves. In pursuing his governing agenda, disagreements will arise over deeply held beliefs, and the arguments are bound to get heated. But, unlike his predecessor, Mr. Biden knows the difference between opponents and enemies.

Mr. Trump has stoked cultural conflict — by, for instance, declaring war on N.F.L. players who kneel during the national anthem. Mr. Biden presumably will find better uses of his time and energy. Not every culture-war skirmish merits presidential involvement, and many would be better managed without it. QAnon may be a disturbing sign of the times, but it does not yet rise to the level of a presidential talking point. Neither do the “thin blue line” flags that are a sign of police solidarity and, depending on whom you ask, white supremacy.

With the coronavirus holding center stage, even core culture-war issues — abortion, L.G.B.T.Q. rights, religious freedom, assault weapons — may wind up relegated to the political background. There will be movement on all of these issues outside of Mr. Biden’s control, either in Congress or the courts. But he need not celebrate or mourn each of these developments as an existential victory or defeat. Not because they aren’t important, but precisely because they incite such passion and fury. All of these questions will be contested long after Mr. Biden’s term in office is over. These long-simmering challenges will still be there, waiting, when the acute trauma of the pandemic has passed and the nation begins its recovery.

Mr. Biden has the temperament and the tools to moderate rather than maximize conflict. When the death of George Floyd this spring sparked nationwide protests over racial injustice and police brutality, forcing those issues to the forefront of the presidential race, Mr. Trump sought to inflame tensions. Who can forget his Twitter invocation of the civil rights-era phrase, “When the looting starts, the shooting starts”?

Mr. Biden took a different approach. He acknowledged America’s entrenched racism and stressed his support for police reform, even as he rightfully rejected the edgier calls to “defund the police.” He reached out to the victims of and the families impacted by police violence, offering comfort and understanding, and he sympathized with the frustration and anger of the protesters. But he also condemned the pockets of violent rioting that accompanied some protests. His goal was not to downplay the problem but to lower the temperature on a crisis that threatened to consume the nation.

Nowhere has the bleed of culture wars into politics been deadlier than in what should have been a wholly apolitical matter: the handling of the coronavirus pandemic. Historians will puzzle over the idea that mask-wearing in service of protecting all citizens was considered by many to be a mark of oppression. Imagine if supporters of free trade or the Green New Deal decided to shun wearing seatbelts, as a political statement.

The pandemic is a public health emergency requiring precautions and sacrifices. Yet Americans are also weary of those sacrifices and depressed and frustrated by having their lives turned upside down. As president, Mr. Biden can express empathy with such exhaustion, while standing firm on the necessity of ongoing safety measures. He can continue to model good behavior, like mask-wearing and social distancing. He can decline to host potential super-spreader events in the Rose Garden. Other members of his administration can be directed to follow suit. A national mask mandate might not be feasible at this point, but calling on government workers to observe basic safety precautions is well within the president’s authority. If Americans see their leaders working to keep the public safe, they may be more willing to do their part.

If, as seems likely, the new president inherits a divided government, some of the more ambitious items on many of his supporters’ wish lists will have to be set aside for now. As a candidate, Mr. Biden won plaudits for his listening skills and for his outreach to former rivals. Once in office, he’ll need to keep the lines of communication wide open and ensure that his restive base does not feel taken for granted.

Pretty much every move Mr. Biden makes will disappoint some constituency. Such is the nature of the presidency. His persistent challenge will be to deal with all parties respectfully, bringing people into the conversation and making them feel heard. Even when his outreach efforts fail, they will send a message about how he views his job.

“Let’s give each other a chance,” Mr. Biden pleaded in his Nov. 7 victory speech. “It’s time to put away the harsh rhetoric. Lower the temperature, see each other again, listen to each other again. And to make progress, we have to stop treating our opponents as our enemies. They are not enemies. They are Americans.”

America’s divisions predate Mr. Trump, and they will outlast Mr. Biden. But there is progress to be made. And there is value in the very act of trying.

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