I was wrong about Joe Biden.

In his inaugural address a year ago this week, Biden pledged to pour his “whole soul” into “bringing America together” and “uniting our people.” He urged Americans — sincerely, I believed — to “see each other not as adversaries but as neighbors,” to “treat each other with dignity and respect,” and to “join forces, stop the shouting, and lower the temperature.”

Far more than any previous president, Biden emphasized unity at his inauguration; it was the core and quintessence of his first speech as the nation’s chief executive. True, nearly all presidents talk about bringing Americans together and rising above partisanship, but it seemed to me that Biden really meant it. I thought so for two reasons:

First, it was what he had campaigned on. Biden’s most important message as a candidate for president was that he was no Donald Trump, stoking anger, demonizing critics, and widening the political rift. Rather, Biden said, he would bring to the White House his experience of working with legislators of both parties and fashioning compromises to get things done. With the possible exception of his vow to “shut down” the coronavirus, Biden’s central promise was that he would be the political healer America needed — a “president who doesn’t divide us but unites us … who appeals not to the worst of us but to the best.” During the home stretch of the 2020 election, that was Biden’s closing pitch to the electorate: not a policy agenda but a commitment to lead Americans in freeing themselves “from the forces of division … that pull us apart, hold us down, and hold us back.”

Second, in the days following his election, Biden not only kept stressing the need to achieve cooperation, unity, and less ferocious political discourse, but also explicitly identified that as his mandate. “Now that the campaign is over,” asked the president-elect, “what is our mandate?” His answer: “Americans have called on us to marshal the forces of decency and the forces of fairness… . Let this grim era of demonization in America begin to end — here and now.”

That was exactly right, not just as moral sentiment but as hard-headed political analysis. Voters had elected Biden by a comfortable margin in both the popular vote and the Electoral College, even though a solid majority, 56 percent, said they were better off than they had been before Trump’s election. On the issues, more Americans agreed with Trump than with Biden. It was his character that cost Trump the election. His obnoxious, bellicose, divisive, unpresidential behavior — that was what most of the nation wanted no more of. Biden’s mandate was clear: to not be Trump and to usher in a period of reconciliation.

Given the centrifugal forces invariably unleashed by politics in a society as evenly divided between two parties as America is these days, maybe that was always a pipe dream. But Biden never tried.

Hardly had the fine words of his inaugural address receded in the rearview mirror than his commitment to healing and peacemaking faded. Soon it became clear that the new president had yielded to the temptation to push the sweeping, expensive, transformational agenda championed by his party’s left-wing base — vast new spending measures, statehood for the District of Columbia, a student debt bailout, higher corporate taxes, a major expansion of the welfare state, and much of the radical Green New Deal. Biden was “a proud moderate during his three and a half decades as a senator, but he has fallen in firmly with the progressives as president,” concluded The Atlantic in September. And the further leftward he moved, the more intolerant his rhetoric became.

With his “voting rights” speech in Georgia last week, Biden hit an atrocious low. The president who a year ago had beseeched Americans to see those with whom they disagree “not as adversaries but as neighbors,” to “stop the shouting and lower the temperature,” loudly slammed 52 senators who won’t back his call to blow up the filibuster and pass his party’s aggressive election bills as “domestic enemies” and acolytes of George Wallace, Bull Connor, and Jefferson Davis. His language was so unhinged and intemperate that even his ally Dick Durbin, the Democratic Senate majority whip, deplored it.

At the one-year mark of his presidency, Biden is failing utterly at the singular task he set himself: to bring the nation together. In a new Quinnipiac poll, a plurality of Americans (49 percent) say that he is doing more to divide the country than unite it. Fully 64 percent of respondents in a CBS News-YouGov survey released Sunday say the word “unifying” cannot be applied to Biden’s presidency. The president’s failure is reflected in his own unpopularity: Just 33 percent of the public approve of the job he is doing, while 53 percent disapprove. I really expected better of the man. My bad.

(Jeff Jacoby is a columnist for The Boston Globe).