The former South Carolina governor and ambassador to the United Nations, Nikki Haley, is telling President Trump to “quit whining” about Vice President Harris. Such sharp talk by a critic offers a contrast to those like Senator Vance, Trump’s running mate, and spotlights a possible turn for the GOP.

Ever since Democrats swapped in Ms. Harris, Trump has criticized it as a “coup.” He feels cheated out of his preferred matchup with President Biden, but many teams have game-planned for one quarterback only to find the backup under center after kickoff. The game still gets played, and one team doesn’t get to pick the other’s roster.

“What Donald Trump needs to do,” Ms. Haley said Tuesday on Fox News Channel, “is go out there and campaign every single day, telling the American people exactly what Kamala Harris has said.” With “80-plus days” until the election, she stressed discipline, a quality for which even Trump supporters have yearned.

As journalist Finley Peter Dunne’s character, Mr. Dooley, said in 1895, “Politics ain’t beanbag.” What Democrats did may seem unfair to Team Trump, but so did the first forward pass in football. The British Red Coats seethed that the Continental Army employed guerrilla tactics rather than lining up for a civilized exchange slaughter by grapeshot.     

All is fair in love, war, and politics. Trump himself is defined by going off script, preferring tangents to teleprompters. No one reaches the Oval Office without that self-confidence. “I’m president,” as Trump told a Time reporter in 2017, “and you’re not.” President George H. W. Bush, whose temperament was the opposite of Trump’s smash mouth, often used that exact retort.

So, why did Ms. Haley risk angering Trump with advice sure to fall on deaf ears? “We need him to win,” she said, “but you’ve got to go out and do the work, and the one thing Republicans have to stop doing: Quit whining about” Ms. Harris. “We knew it was gonna be her.”

Of GOP complaints that Ms. Harris refuses to take questions from the press, Ms. Haley said, “She’s not gonna give an interview” and Democrats would “hold out as long as they can. That’s their right; they can do it. That doesn’t mean we can’t talk about what she believes in, and we should be getting out there and doing that.”

Trump rode tweet storms to the White House, and highlighting Ms. Harris’s record would be a break with that. It would also run counter to the zeitgeist that everyone should complain about everything all the time. The press rewards that kind of outrage, conferring power on those who take offense.

Whining gets amplified more than policy. A common social media tactic demonstrates this fact. Digital strategists advise including wrong dates, falsehoods, or deliberate misspellings in posts. The errors bait trolls to comment, gaming algorithms by boosting engagement to harvest clicks.

At a press conference on Thursday, Trump defended his right to trade “personal attacks” with Ms. Harris.  Ms. Haley, though, makes a case for a different strategy. She’s now a bigger blip on the radar as a replacement for Mr. Vance should he stumble or should Trump decide to call his own Hail Mary to discombobulate Democrats.

Instead of griping, Ms. Haley’s counter strategy aligns with the 2nd Marine Division’s motto: “Improvise, Adapt, Overcome, then Adapt Again.” Trump can leave it to people in the stands to shout about unsportsmanlike conduct. He’s the one on the field taking the snaps.

“Running as victims … won’t win Republicans any votes,” I wrote for the Sun a while back. With a truncated campaign, every second the GOP spends complaining about the Democrats inserting their backup is one they don’t spend trying to score points with higher-percentage plays. All the while, Election Day ticks closer.

Ms. Haley is a lone voice among Republicans pointing at the game clock. Trump may ignore her advice and, once again, win by unconventional means. Yet should he lose, the GOP will be looking for a new play caller — and folks in the stands will remember who warned that whining would allow Ms. Harris to walk into the end zone.