The question of support for the nation’s military moved to the center of the campaign Friday as Democrat Joe Biden and President Trump clashed over allegations in a magazine article this week that the president had called dead American service members “suckers” and “losers.”

Biden lambasted the president’s purported remarks as “disgusting” and “un-American” and accused him of having demonstrated “no loyalty to any cause but himself.” He demanded that Trump apologize to the families of fallen troops. Trump denied the report and called it a “hoax.”

“Who the heck does he think he is?” said Biden, whose late son Beau served in Iraq with the Delaware National Guard. “How would you feel if you had a kid in Afghanistan right now? How would you feel if you lost a son or daughter, husband, wife? How would you feel, for real? But you know in your heart, you know in your gut: It’s deplorable.”

The White House mobilized rapidly in hopes of preventing the debate from becoming “a major election issue,” one senior official said. More than 10 current and former senior aides — including national security adviser Robert O’Brien and senior adviser Jared Kushner, the president’s son-in-law — vehemently denied the Atlantic’s account of the president’s trip to France in 2018.

The magazine, citing four anonymous sources, reported late Thursday that Trump had called off a trip to Aisne-Marne American Cemetery, resting site of American and other troops who died in World War I, because he did not want rain to mess up his hair and he believed it was not important to honor the fallen service members.

But Trump’s aides offered personal testimonies of the president’s concern for the well-being of troops during tactical military operations and his personal attention to wounded veterans during trips to Walter Reed National Military Medical Center and Dover Air Force Base.

“It’s a hoax … just like Russia, Russia, Russia,” Trump said of the magazine’s account at a Friday news conference, comparing it to the special counsel’s investigation into his 2016 campaign’s contacts with Russian operatives. “There is nobody who feels more strongly about our soldiers, our wounded warriors, our soldiers that died in war, than I do.”

The issue has escalated quickly as Biden and his surrogates have sought to undermine a key pillar of Trump’s reelection message — his projection of toughness and patriotism. Trump has boasted of a deep well of mutual admiration and support from military troops and families, while attempting to paint Biden as weak and unable to stand up to foreign leaders. Biden’s campaign seized on the fallout of the Atlantic report to sketch the picture of a president who has a history of mistreating troops and veterans in service of his own political gain.

White House press secretary Kayleigh McEnany disclosed an email from a military officer on the day Trump had been scheduled to visit Belleau Wood stating that bad weather had grounded Marine One, as Trump aides had stated at the time.

Aides said they elected not to have the president take a lengthy motorcade due to the challenging logistics, an account backed up by former national security adviser John Bolton in his recent memoir.

McEnany slammed the Atlantic’s reporting as “conspiracy-laden propaganda” peddled by “liberal activists” that was based on “four cowardly anonymous sources that probably do not even exist.”

Trump said the Secret Service is preparing a report documenting how the trip to the cemetery was canceled due to logistical complications.

“I said nope, ‘I want to go. I insist on going,’” Trump said he told Secret Service officials. “It would have taken us forever. The Paris police said, ‘Please, you can’t do this.’ They’d have to shut down parts of Paris. It was an impossible situation.”

Still, the White House found itself on defensive footing as more potentially damaging allegations emerged about Trump’s views of the military, including on Fox News, the cable network that Trump has relied on for favorable coverage. One Fox correspondent reported that Trump had told aides — while planning for an Independence Day celebration on the National Mall last year — that the inclusion of wounded veterans was “not a good look” and that “Americans don’t like that.”

One former senior administration official told The Washington Post that John F. Kelly, a retired Marine general who was serving as Trump’s chief of staff during the trip to France, grew frustrated on a regular basis with Trump’s lack of basic knowledge about the military and its operations.

A second former official said Trump would occasionally speak disparagingly of the military, angering Kelly and Jim Mattis, another retired general who served as defense secretary. That former official said Trump often praised top military officials and liked surrounding himself with commanders in uniforms. But the president also would complain that the military leaders were myopic and did not understand the business world he had come from, including the importance of profits and losses.

The president would occasionally say that people who served in Vietnam should have been smarter to avoid it, said the second former official.

“He would tire of all the great commendations that people who had fought and served got,” said the second official.

Both former officials spoke on the condition of anonymity to discuss sensitive private conversations. Kelly declined to comment.

At the Friday news conference, Trump ripped into Kelly, deriding him as unable to meet the demands of his White House job. “He was a tough guy,” Trump said. “By the time he was done, he got eaten up. He was unable to function.”

White House aides reached out to former officials and others on the Belleau Wood trip to deny the story, one person familiar with the matter said, and aides are fearful that former military officials will continue to dribble out negative details until the election.

Trump on Friday also reversed a move by the Pentagon to kill funding for Stars and Stripes, the venerable military newspaper. “The president was already facing blowback from the military and it didn’t make sense to do this,” one senior administration official said.

O’Brien, who served as the State Department’s top hostage negotiator before taking over the National Security Council last year, said Trump showed acute sensitivity to the care for service members and their families. He said the president would ask if U.S. troops could be kept out of some military operations, and he cited Trump’s push to increase funding for the military as an example of his willingness to provide the Pentagon “every tool necessary.”

“I can’t believe a word of what’s in the Atlantic article,” O’Brien said, “because I’ve had 2½ years working side-by-side with the president. I’ve never seen anything like that.”

But Biden did not limit his criticism to Trump’s purported remarks in France. Rather, he laid out a litany of examples to build a case that the president’s professed admiration for the Armed Forces is based on political expediency.

Biden cited Trump’s disparagement of the late senator John McCain (R-Ariz.), who was held captive during the Vietnam War, as a “loser”; his description of concussion-like symptoms of U.S. troops in Iraq after a missile attack by Iran in January as “not very serious”; his decision not to confront Russian President Vladimir Putin over U.S. intelligence reports that Moscow had bribed Taliban forces to kill American troops; and the efforts by military leaders to drape a flag over the name of the USS McCain battleship in Japan ahead of Trump’s trip there last year.

“I just think it is sick. It is deplorable — so un-American, so unpatriotic,” Biden said.

Biden’s campaign also arranged a conference call for reporters with Sen. Tammy Duckworth (D-Ill.) and Rep. Conor Lamb (D-Pa.), both military veterans, as well as Khizr Khan, the father of an American service member killed in the Iraq War in 2004, who has been critical of Trump.

“I’d take my wheelchair and titanium legs over Donald Trump’s supposed bone spurs any day,” said Duckworth, who lost both legs during a rocket attack by Iraqi insurgents in 2004. She was referring to the medical diagnosis that reportedly led to a young Trump gaining a medical deferment from service in Vietnam in 1968.

In districts across the country, Democratic congressional candidates seized on Trump’s comments and chided Republican opponents for refusing to stand up to the president. Nearly every Senate Democratic challenger — including many who served in the military — tweeted about the Atlantic report.

“As the mother of a son in the Army, this hit close to home — these reports are deeply alarming,” wrote Theresa Greenfield, who is challenging Sen. Joni Ernst (R) for her Iowa seat.

The Democratic Senatorial Campaign Committee issued a statement that “not a single Senate Republican has spoken out about Trump’s vile attacks against veterans and service members.”

Sen. Martha McSally (R-Ariz.), who was appointed to McCain’s seat after he died in 2018 and faces a challenging race, came closest — praising McCain without explicitly mentioning Trump.

“Senator McSally has no interest in moderating a fight between The Atlantic and the president over anonymously sourced accusations that have been debunked on the record,” a campaign spokeswoman said.

Michael Scherer in Washington and Annie Linskey in Wilmington, Del., contributed to this report.