But there remains one marker by which Mr Trump believes his campaign is showing its true vitality in the home stretch and demonstrating why he can win again on 3 November – crowd size.
Mr Trump has returned to the campaign trail with gusto after battling the novel coronavirus, holding daily rallies with thousands of supporters at airport hangars, including events in recent days in Florida, Georgia, Michigan and Wisconsin. In doing so, the president is again flouting warnings from doctors – including Anthony Fauci, the federal government’s top infectious-disease expert – about the potential health risks of large groups gathering with little social distancing and many eschewing face masks.
For Mr Trump, however, the rallies are a show of strength and an ego boost after months of stumbles, during which former campaign manager Brad Parscale was demoted in part over his management of a rally in Tulsa, Oklahoma, at which turnout was far below projections.
“Can you believe how many people are back there?” Mr Trump asked a crowd Friday in Ocala, Florida, after disembarking Air Force One, which remained parked just beyond the stage for a dramatic flair. Pointing toward reporters, Mr Trump said: “You want to turn the cameras around to show – that is a lot of people here today. They never report that.”
For Mr Trump, a former reality television star, the size of the audience has long been paramount, a measurement he believes foreshadowed his 2016 upset victory over Hillary Clinton and one he consistently touts as evidence that the pollsters and pundits who are increasingly pessimistic about his reelection chances are wrong again.
During his debate with Mr Biden – whose campaign has featured smaller groups of supporters, with more adherence to coronavirus safeguards – Mr Trump said mockingly: “Nobody shows up to his rallies.”
By contrast, he added, “we have tremendous crowds, as you see, and literally on 24 hours notice.” He boasted of crowds of 35,000 to 40,000, although the actual count has appeared far smaller. His campaign declined requests to provide attendance figures.
On social media, the president and his allies have flooded their feeds with panoramic photos of the crowds and video footage panning the scene from above, some scored to dramatic music.
“The Polls are Wrong!” Mr Trump’s son, Eric, tweeted Saturday, showing crowd footage from an airport rally in Macon, Georgia.
In many ways, the president is running a replay of his 2016 campaign, in which he taunted his opponents as having less enthusiastic supporters. But Democrats argue that the 2020 campaign offers significant differences and that Mr Trump is fooling himself.
Experts said rallies can be helpful in energising supporters, as well as collecting their personal data to help with fundraising and get-out-the-vote efforts. A Washington Post-ABC News poll last week found that 71 per cent of Trump supporters said they are “very enthusiastic” about supporting him, well above the 52 per cent of Biden supporters who are very enthusiastic about the former vice president.
But Mr Trump’s enthusiasm advantage may not contribute to an actual turnout advantage. The Post-ABC poll found 90 per cent of registered voters who support Mr Trump said they are absolutely certain to vote or have already done so, as did 88 per cent of Mr Biden’s supporters.
Overall, Mr Biden leads Mr Trump by 11 points in a Post average of national polls and by between seven to eight points in Wisconsin, Michigan and Pennsylvania, the three swing states that propelled Mr Trump to the White House in 2016.
Meanwhile, Mr Biden and his Democratic allies raised a record $383 million (£296.6 million) in September, far outpacing the $248 million (£192 million) accumulated by Mr Trump and the Republicans.
Yet the president has settled on a closing message that appeals narrowly to his base.
In his stump speech, which usually lasts more than an hour, Mr Trump has touted unfounded conspiracy theories about Mr Biden, Ms Clinton and former president Barack Obama, played down the threat of the pandemic and pushed the Senate to confirm conservative judge Amy Coney Barrett to the vacant Supreme Court seat.
At times the rallies stray into potentially dangerous territory. On Saturday in Muskegon, Michigan, Mr Trump amplified his previous attacks on Democratic Governor Gretchen Whitmer by demanding that she relax coronavirus safety restrictions on businesses and reopen schools, promoting the crowd to chant, “Lock her up!” Trump didn’t move to stop them and instead responded with a smirk: “Lock ’em all up.”
The governor – who the FBI said was the target of a kidnapping plot from an extremist group that federal authorities broke up last week – slammed the president for using “exactly the rhetoric that has put me, my family and other government officials’ lives in danger while we try to save the lives of our fellow Americans.”
Democrats said Mr Trump was hurting his own cause.
“From a message standpoint, all rallies are not helpful rallies,” said David Axelrod, the CNN political analyst who served as a key strategist on Obama’s 2008 campaign.
“It matters what you say,” Mr Axelrod said. “Mr Trump treats rallies like a stand-up act for the faithful. But, beyond thrilling the already devoted, if his message is off-key for the larger electorate, who see only his spiciest or most controversial lines, the rallies may only exacerbate his problems. America may be tired of the show.”
Mr Trump is still thrilled by it. Along with his rallies, he has touted pro-Trump boat parades and Trump campaign yard signs and flags as evidence that he remains popular in swaths of the Rust Belt and Florida’s endless subdivisions.
“The rallies are not the be-all, end-all by any stretch,” said Charlie Gerow, a Pennsylvania-based Republican political strategist. “But they are an important show of strength to rally the base and increase the intensity of those people. Folks who attend a rally go home, talk to friends, talk to neighbors, talk to their family about what happened … Mr Trump has thousands of little ambassadors going to their little corners of America, and the Biden campaign doesn’t have that.”
Mr Biden faced similar doubters during the Democratic primary, as rivals – most prominently Senator Bernie Sanders – staged larger rallies with what appeared to be more passionate supporters. But Mr Biden stuck to his strategy and ultimately prevailed on the strength of overwhelming support from African American voters, who analysts said have traditionally not attended rallies as frequently as white voters do.
During the pandemic, Mr Biden has proceeded more cautiously than Mr Trump. The former vice president has held smaller gatherings indoors, where he and supporters wear masks, as well as outdoor “drive-in” events at which supporters park their vehicles in socially distanced spaces to listen to him speak from a stage.
On Friday, Mr Trump retweeted a video posted by an NBC News reporter that showed Trump supporters, gathered in a group, chanting “Four more years!” and “Trump!” from a distance as Mr Biden addressed a few dozen supporters in Toledo.
Mr Biden aides defend the approach by accusing Mr Trump of recklessly endangering himself, his staff and his supporters with his larger rallies.
“Mr Trump’s pandemic response continues to fail American families,” Biden campaign spokesman Andrew Bates said, “yet the president is knowingly endangering his own supporters out of insecurity and vanity.”
Trump campaign aides emphasized that his rallies generally take place at least partially outdoors. They said supporters have their temperature taken as a precaution and are offered face masks and hand sanitizer.
In Ocala on Friday, thousands waited for more than two hours for the president’s arrival on Air Force One. On a video live stream, correspondent Lilit Vanetsyan of Right Side Broadcasting, a conservative pro-Trump network, marveled at the scene: “It is electric out here. I mean, you show me a Biden rally that looks like this.”
Many in the crowd behind her were not wearing masks.
Last week, Dr Fauci, the director of the National Institute of Allergy and Infectious Diseases, called Mr Trump’s rallies “very troublesome” at a time when coronavirus infection rates in the United States have risen to their highest levels since July.
Ken Farnaso, the Trump campaign’s deputy national press secretary, rejected criticism of the events as risky.
“With just under 20 days to go until Election Day, voters deserve to see both candidates on the trail working to win every single vote, and it’s clear that everywhere President Trump goes, support of this ‘America First’ agenda goes unmatched,” Mr Farnaso said.
But Mr Trump’s obsessive focus on speaking to large groups took a hit Friday – a day after he and Mr Biden had participated in duelling town hall-style television forums on competing networks.
The ratings showed that Mr Biden had bested him, drawing an average of 13.9 million viewers to the president’s average of 13.06 million.