Whatever Bernie Sanders cares to admit, the Democratic primaries are effectively over: It’s ex-Veep Joe Biden challenging President Trump this November — in what’s plainly going to be the weirdest campaign ever.

With the nation gripped by the coronavirus crisis, each side needs to mute the normal no-holds-barred attacks: We’ve got to settle our differences in a more civilized manner, because we’re all trying to stick together even as we disagree.

That doesn’t mean the two sides won’t be going at it in the battleground states from Arizona to Pennsylvania to Florida. But the rest of the nation will see less of that heat than otherwise from the campaigns and even most officeholders — leaving most of the acid to the media, much of which will continue sniping at Trump.

One clear bonus for Biden: The epidemic will basically eliminate traditional, in-person events. That not only takes out the president’s favorite way to campaign, it relieves his challenger of the need to be out there every day — something that plainly tested his limits during the primaries, as the 78-year-old regularly showed signs of fatigue.

Indeed, the new reality left Biden in his best form yet for his last debate with Sanders, by far the sharpest he’d been in months of these exercises.

More, the crisis reduces the electoral value of everything Trump has achieved: Even more than usual, voters won’t focus on what’s already been delivered (i.e., a stronger, more prosperous nation where working-class wages have been rising faster than the incomes of the better-off), but on what’s ahead: Who’s better to lead us out of this mess?

This is an added test for the president as he handles the crisis: He needs to reassure the public while leveling with it — and signal that he’s on top of the challenges to come.

It will be up to others, mostly, to point out why Joe Biden isn’t the man to move America forward: His back-slapping charm worked fine as the wingman to a more reserved President Barack Obama, but Biden has never been an actual leader — unless you count his management of the Senate Judiciary Committee during things like the Clarence Thomas confirmation hearings.

And even his time as Obama’s point man on various issues will be tainted by the way son Hunter and other family members routinely found a way to cash in on “Uncle Joe’s” assignments.

Thus, in the battle for swing voters such as suburban women, the crisis is a problem for Biden, too: These undecideds are no longer looking at which candidate’s manner is most grating, but at which one can actually handle entirely unprecedented challenges.

So every time Biden takes one of his walks down memory lane to tell of how he handled some past controversy, he’ll raise questions of whether he can adjust to this new world.

Certainly, his repeated insistence that Americans shouldn’t see China as a hostile rival, that we should trust Beijing as a partner in an open, globalist economy, won’t play very well.

In some ways, this campaign still resembles the 2012 and 2004 races: It features a controversial incumbent and a challenger who in many ways is a generic representative of his party’s conventional wisdom. But those contests came years after the peak crises of 9/11 and the 2008 meltdown; this one will come when the WuFlu challenge is still fresh, and when the nation is looking for post-crisis vision and leadership to get it back on its feet and surging ahead.

Both candidates need to offer reassurance but also inspiration. It’s a test neither one was expecting just a week or two ago. America is watching to see who better rises to that challenge.