Donald Trump’s campaign manager Kellyanne Conway sits with Robby Mook, Hillary Clinton’s campaign manager, before Thursday’s forum at Harvard University’s Kennedy School of Government in Cambridge, Mass. (Charles Krupa/AP)

Every four years, the Institute of Politics at Harvard’s Kennedy School of Government assembles the managers of the presidential campaigns for a deep, post-election debrief. It is always illuminating and generally civil, with occasional fireworks. Because the 2016 election was unlike any other, this year’s managers conference was also unlike any other.

In the immediate aftermath of President-elect Donald Trump’s victory over former secretary of state Hillary Clinton, all the leading players said the right things. Trump called for healing and said that he would try to bring the country together. Clinton asked her supporters to give the newly elected president the space and opportunity to govern. President Obama, despite harsh words for Trump through the campaign, said that he would assure an orderly transfer of power in the spirit of reconciliation.

But everyone knew or should have known that the wounds from an election that was as raw and divisive and negative as campaign 2016 would not be quickly healed. That especially includes those who were the principal antagonists, the people who ran the campaigns during the general election. At Harvard’s IOP, it all gushed forth, creating perhaps the most contentious session that this series of conferences, which began in 1972, had ever seen.

The general-election session was the culmination of the two-day conference, which was organized in collaboration with Harvard’s Shorenstein Center on Media, Politics and Public Policy. Earlier sessions plumbed, separately, the Republican and Democratic nomination battles, as well as initial strategic assumptions of the many major-party candidates who sought the White House this year.

On Thursday night, the dinner included a lively conversation among media executives, punctuated by dissenting interjections from the audience, about the role of the news media, a topic that will be a continuing focus of debate as the new Trump administration takes and exercises power. Overall the sessions were tame, until the final Thursday afternoon, when the pent-up fury of the campaign finally erupted.

Hillary Clinton’s communications director, Jennifer Palmieri, aboard Clinton’s campaign plane on Nov. 6. (Andrew Harnik/AP)

My colleagues Karen Tumulty and Philip Rucker provided a full account of what transpired when the leading advisers for Trump and Clinton sat across the table from one another for 2 1/2  hours to offer a historical rough draft of how the general election campaign unfolded. The headline on their story described it as a “shouting match.” (For the sake of full disclosure, I helped to moderate the general-election session, along with NBC’s Andrea Mitchell and BuzzFeed’s Katherine Miller.)

What captured the biggest headline was an explosive exchange between Clinton communications director Jennifer Palmieri and Trump campaign manager Kellyanne Conway over whether the Trump team had run a campaign that had empowered the voices of white nationalists. Palmieri bluntly said Trump had done so and that she would rather have lost the election than run a campaign the way she asserted Trump did. Conway angrily stood her ground, denying the charge and contending that Clinton lost through her own inadequacies, as she and Palmieri spoke over and past each other.

The combination of pain and resentment toward Trump among Clinton advisers was never much below the surface. This was an election that the Democratic nominee expected to win in what would have been a history-making event. Her advisers were confident of that victory until the moment late on the night of the election when their path to 270 electoral votes had been finally blocked by Trump’s breaching of the “blue wall” in the Northern industrial states. They were devastated by the loss.

Campaign manager Robby Mook’s explanation of why Clinton lost focused heavily on the intervention by FBI Director James B. Comey in the final 10 days. Mook said Comey’s twin moves concerning the FBI’s probe into Clinton’s emails contributed significantly to the outcome, noting that late-deciders broke far more for Trump. He also acknowledged shortcomings by the campaign, including a failure to produce the kind of support among key parts of the Obama coalition — whether young voters, suburban women or African Americans — that the campaign had estimated she would need to win.

What Mook and his colleagues found difficult to acknowledge, in part because they were there to shield their candidate from too much blame, was Clinton’s weakness as a candidate and the hostility that she had engendered — fairly or unfairly — over a long period of time that hampered her ability to connect more effectively with enough voters. That will remain an important, if not fully measurable, aspect of what cost her the election — and it was something Trump’s team was determined to assert throughout the discussion.

If there was pain and resentment on the Clinton side (along with some expressed respect for what Trump’s team pulled off), there was another emotion that emanated from Trump’s advisers, an expression of grievance born of an apparent feeling of a lack of respect for what their candidate had done after so many said he was destined to lose. The same combativeness that marked the election was on display time and again during the discussion from Trump’s side of the table — an anti-establishment sentiment of us-vs.-them that will probably animate Trump’s presidency.

President-elect Donald Trump's chief White House strategist Stephen K. Bannon decided not to attend an event at Harvard University's Institute of Politics, but protesters took to the streets of Cambridge, Mass., Nov. 30, regardless. (Twitter/Eli Gerzon of Jewish Voice for Peace)

There’s no question that the newly elected president scored a great upset and deserves credit for running a far more shrewd campaign than his critics contended throughout the election. Some of those who attended the Harvard sessions as observers said afterward that the Trump team demonstrated more competence and skill as they discussed what happened than some of the caricatures of the operation as the contest was unfolding.

But Trump’s victory, however shocking to those who never anticipated it, was no landslide, as some of his advisers have claimed. He won 306 electoral college votes. While that is better than George W. Bush managed in both of his presidential campaigns, it is a smaller number than in the victories by Obama, Bill Clinton, George H.W. Bush and Ronald Reagan.

Beyond that, Trump now trails in the popular vote by almost 2.6 million votes, or 1.9 percentage points, according to compilations posted by David Wasserman of the Cook Political Report. Trump’s breakthrough victories in Pennsylvania, Michigan and Wisconsin, which sealed his victory, were each by less than a percentage point and by a combined total of fewer than 80,000 votes.

All that became another flash point over whether Trump had won a true mandate. When the Clinton team said no, Trump advisers bristled in response. We won, they said. Case closed.

As the campaign managers were delivering their analyses Thursday afternoon, Trump was on the road to begin a series of rallies to thank his supporters. He started in Cincinnati, and it was as if the campaign had never ended, with the buoyant president-elect reveling in his victory.

Chants of “lock her up” echoed through the arena when he mentioned Clinton, and he laced his speech with another attack on the “dishonest” news media. Outside the arena, protesters signaled their unwillingness to reconcile.

So it should have been no surprise that, in the conference room at Harvard University, the tensions between the two sides were so vividly displayed. The emotions are testament to the deep divisions that will continue to exist and to the long and challenging road ahead for the 45th president and for the country he will govern.