So much for unity.

Donald Trump could have done himself and the divided country a lot of good had he simply thanked Joe Biden for his service and wished him well.

Instead, he blew it.

All he had to do was act the nice guy and show President Biden some respect for acknowledging that, after a lifelong career in government and politics, he was withdrawing from the presidential campaign in the best interest of the country.

It would have been a decent thing to do, even if he didn’t mean it. It would have shown class and character, of which the anti-Trump crowd claims the former president has neither.

And it might also have attracted favorable attention from half the people in the country who, policy aside, take issue with Trump’s crude and rude political behavior.

These are the millions of unpolled Americans who may agree with Trump’s policy but are turned off by his personality.

They are the Americans who would vote for Trump if only he would only stop talking, calling opponents juvenile names and insulting people. Trump talks them out of voting for him.

And while Trump gained a lot of sympathy and support from Americans who were impressed by his heroic reaction after being shot — and his fleeting reference to the need for unity — it all quickly evaporated.

Trump’s pomposity pushed everything aside as he acted, with Biden out of the race, as though he had just been re-elected.

And, instead of issuing a few civilized remarks about Biden and his decision to drop out of the race and endorse Vice President Kamala Harris, Trump could not restrain himself.

Hardly had Biden issued his announcement that he would not seek re-election, then Trump reverted to his brutalist political verbiage by figuratively kicking Biden in the head as he lay helpless on the ground.

Trump shoots the wounded and relishes it.

Even heavyweight boxers shake hands after a grueling 10 or 15 round fight after beating the hell out of each other.  In this case Biden was so out of it he could not even answer the bell.

Trump no doubt has his own good reasons to continue his campaign against “Crooked Joe.”  It was Biden who ousted him from the White House in 2020.

Trump is the type of man who remembers a slight from the first grade, let alone after losing a “rigged” election to Joe Biden.

And it is true that Trump answered in kind to Biden and the Democrats who called and are calling him Hitler and a threat to democracy, as well as to the Biden inspired weaponization of the U.S. Justice Department that went after him.

It also embarrassed Trump when the government he once headed sent armed agents to raid his Mar-a-Lago home and confiscate top secret documents, like the documents that Biden had laying openly around in his garage in Wilmington, Del. for years.

But Biden is out of the picture. He was sent reeling after the debate with Trump and never recovered, but got only worse.

So why go after him as opposed to letting him sail off into the sunset?

Because Trump is Trump and needs someone to hate, even if it costs him votes.

This is not to suggest that Trump be invited to speak at Joe Biden’s retirement party and present him with a set of golf clubs. But it would have been refreshing — and probably good for his soul, as well as the soul of the country if he took a kinder and gentler approach to Biden’s departure. Biden may not have been an effective president, but he was an American one, and not president of Russia or the leader of China, Iran or North Korea.

Hardly had Biden announced his decision, though, then Trump posted his tribute: “Crooked Joe Biden was not fit to run for President and is certainly not fit to serve — and never was.  He only maintained the position of President by lies, Fake News, and not leaving his Basement. All those around him, including his Doctor and the Media, knew that he wasn’t capable of being President, and he wasn’t.”

So much for unity.

Peter Lucas is a veteran political reporter. Email him at: peter.lucas@bostonherald.com

President Joe Biden walks out of the Oval Office of the White House.