Donald Trump has advertised that he plans to bring back winning. America will win so much, he says, that we’ll get “tired of winning .”

But that’s not what Americans need from our political leadership right now. We need someone who can bring back losing.

Specifically: the art of losing graciously.

The everyone-gets-a-trophy culture supposedly pervasive among millennials, and so often ridiculed by pundits, seems to have infected our political class. Politicians on both sides of the aisle — from Trump and Bernie Sanders on down — have apparently become accustomed to being told they’re right, righteous and victorious all the time.

Perhaps as a result, they have become unable to admit either defeat or even simple wrongness.

Democratic presidential candidate Hillary Clinton was cleared of wrongdoing by the FBI into her email practices while at the State Department. Republican foe Donald Trump took aim at Clinton at a rally July 5. Here's what he said. (Victoria Walker/The Washington Post)

America, in short, is led by a coterie of sore losers.

Unhappy that the FBI’s investigation into Hillary Clinton’s email server resulted in no indictment?

Don’t acknowledge defeat and move on with your life! Instead, reverse your previous statements about accepting the integrity of the FBI’s investigation, as Rep. Jason Chaffetz (R-Utah) did, and pummel the agency director in a public hearing about his judgment, biases and secret agenda.

Or alternatively, take a cue from Rep. Darrell Issa (R-Calif.), and threaten to shut down the entire federal government until you get your desired indictment.

Lost a state’s primary? Multiple state primaries, even? Then declare that the system must be rigged against you, as both Sanders and Trump argued for much of the past year. Nearly a month after the last primary, foreclosing him from the Democratic nomination, Sanders still can’t bring himself to acknowledge his defeat and exit the race.

Trump’s tantrums about the primary process have died down lately, given that he ultimately emerged victorious. But he and his advisers have found other occasions to whine about the unfairness of the system and to demand constant relitigation when things don’t go his way.

He denies the veracity of any poll that shows him trailing Clinton — which is almost every poll. Once waxing rhapsodic at every rally about the beauty of randomized surveys, Trump now denounces them all as “phony.”

Likewise, if Trump disagrees with a judicial ruling, well, that judge is clearly unfair and exhibiting “unwarranted bias toward Trump.” New judge and new ruling, please.

If an analysis of his policy plans notes drawbacks, well, the outfit doing the scoring must be crooked.

If an anti-Semitic image he defended as harmless turns out to have been sourced from a neo-Nazi website, he’s not in the wrong; his critics are, for ever suspecting him of impropriety.

Never back down, never admit mistakes, and never, ever, ever acknowledge defeat. After all, the worst thing on Earth a person can be, in Trump’s view, is a “loser.”

Here’s the thing.

Everyone, at some point in life, makes mistakes, gets things wrong, and, yes, even loses. That might include a bet, an election, a policy vote, a court case or even a verdict on the provenance of a Twitter image.

Losing is never fun; no one claims it is. But neither is it necessarily a sign of moral failing, or that the system is rigged against you. Sometimes the Yankees win, sometimes the Red Sox win. That’s just the way it goes. You pick yourself up and move on.

Maybe, convinced of the nobility of your cause, you get back on the field the next day and try, try again, hoping to learn from your loss and play better the next time. Bully for you if so.

But today’s politicians are not exactly regrouping, restrategizing and reshaping their efforts whenever they suffer a defeat. They’re whining, denying, relitigating and lashing out.

They’re taking their ball and going home. Or worse, they’re sticking around and harassing the umpire.

Our political leaders haven’t always behaved this way.

Look no further for evidence of a gracious, sportsmanlike loser than the Oval Office letter George H.W. Bush left his successor, Bill Clinton, in 1993. In that letter, which went viral recently, Bush wrote: “You will be our president when you read this note,” adding, “Your success is now our country’s success. I am rooting hard for you.”

Today such class and magnanimousness is almost unthinkable, especially after a bitter, nasty campaign.

Come Nov. 8, whoever wins, up to half of the country will find itself on the losing side of the White House race. (Actually, maybe even more than half, if 2000’s popular vote is any precedent.) We voters will look to our leaders to learn how to process our loss (or win), accept it graciously and move forward with our lives.

So far our leaders are providing a poor example.