On Tuesday, Trump stood in the Rose Garden and went on a non-stop nearly hour-long anti-Biden rant, spraying a variety of broadsides at the former vice president, on everything from China policy to immigration to policing and much more. In what may have been his wildest attack, Trump claimed Biden's housing policy would "abolish the suburbs."
Republican and Democratic strategists who spoke with NBC News said it has been tough sledding for the president in blasting his Democratic rival for several reasons.
First, Biden has remained low-key during the coronavirus pandemic, while Trump's handling of it is closely examined daily, they said. Biden is also viewed more favorably than 2016 Democratic nominee Hillary Clinton, who was under investigation during the campaign.
Perhaps most important, Trump was the outsider challenger last time around. Now, he's an incumbent with a record.
"In 2016, he had a very clear message and very clear action items," said Matt Gorman, vice president at the GOP consulting firm Targeted Victory. "He had an elevator pitch on why you should vote for him. He had that in the economy until COVID hit. Now it's harder to find that — especially now that the focus has stuck on him.
"Biden is barely campaigning, so he's not making many mistakes," Gorman added. "Trump was also helped by the fact that Hillary had 20 years of built-in negatives."
In early May, as Trump campaign manager Brad Parscale tweeted that the re-election team was unleashing its "Death Star," Trump trailed Biden by 5 points in the RealClearPolitics polling average. Now, he trails Biden by 9 points, and he is behind in key swing states.
The Trump campaign spent most heavily on TV ads claiming that Biden would be a tool of the far left, that he doesn't have the mental competency to be president and that he's the wrong person to deal with China.
The campaign has spent at least $6.6 million in English and $200,000 in Spanish on an ad imagining a world in which police budgets are slashed — the ad it has spent most heavily on since May, according to Advertising Analytics. The spot contrasts an unanswered 911 call with images of violence at protests and says people wouldn't be safe under Biden with supporters who want to slash police funding.
Recent polling showed that most Americans disagree with Trump on what efforts to defund police departments mean and disapprove of his handling of race relations after George Floyd's death. Biden has said he doesn't support defunding departments, but he has said he's in favor of making federal aid to law enforcement agencies conditional in hope of creating incentives for certain police reforms.
The next biggest ad spend is for a spot arguing that Biden is "slipping" mentally and "is clearly diminished."
The campaign has spent at least $4.2 million in English and $2.3 million in Spanish on the ad since May, according to Advertising Analytics, which shows that the campaign has spent more than $10 million on a variety of ads saying Biden is the wrong choice to deal with China.
Yet a Fox News poll in May reported that more voters trusted Biden on China than Trump. And a Monmouth University poll this month found that more voters felt Biden, 78, has the mental and physical stamina to handle the presidency than felt so about Trump, 74.
The Biden campaign has called many of Trump's attacks mere projection onto their candidate. In a recent memo, deputy campaign manager Kate Bedingfield said as much, pointing to Trump's attacks on corruption, cognitive ability and China, among other subjects.
Biden campaign spokesman Andrew Bates said Trump's "bald-faced lies and desperate, own-goal attacks on Joe Biden only serve to remind the American people of the true stakes of this election and that Trump's instability makes it impossible for him to be the leader we need in this moment."
Trump himself has bounced between Biden messages while faced with nationwide protests and a pandemic that has killed more than 136,000 people in the U.S., recently accusing Biden of being against reopening schools.
"It is difficult to demonize Joe Biden," said former Rep. Carlos Curbelo, R-Fla. "He is certainly not short on flaws, but throughout his career he has never been considered a villain or a shady character. The president almost needs that kind of foil in order to succeed."
Curbelo said Biden's "affable and conciliatory" nature makes it tough for Trump to land punches.
"It's difficult to attack vanilla," he said.
Asked about their most effective line against Biden, Trump campaign spokesman Ken Farnaso said the president "has done more in three years than candidate Biden has done in nearly five decades in Washington" on issues like taxes, trade, immigration and the economy.
"'Promises Made, Promises Kept' isn't just a motto. It's a bold track record of success that this president will build on in his second term," he said.
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At his rally in Tulsa, Oklahoma, last month, Trump slammed Biden for not having written all of the statements attributed to him, saying they are instead written by "professional people, great students in English lit." He also said Biden would "surrender your country to these mobsters," citing leftists.
Republican strategist Matt Mackowiak, president of Potomac Strategy Group, called the Tulsa rally a "missed opportunity" to take Biden to task, saying it was "a meandering grievance session" that featured Trump explaining at length a recent descent down a ramp and why he drank a glass of water awkwardly.
"Trump has to raise Biden's negatives, right?" Mackowiak asked. "If Trump's upside down and Biden's right side up on image, Biden's going to win. Now, can he get Biden to where Hillary was? No, probably not. Biden's just not as detestable as Hillary was, and they don't have the issue that they had with Hillary on the emails and the investigation."
Liam Donovan, an ex-Republican aide now working as a lobbyist, said that while Biden has shortcomings tied to his age and his gaffes, those "flaws are largely shared or otherwise mitigated by Trump himself."
Donovan added that it's difficult to spin Biden as a tool of the radical left given that the Democratic primary campaign was heavily focused on whether Biden was out of touch with progressives on climate, racial and economic issues.
"It took a quarter-century to turn Hillary Clinton into the supervillain foil required for Trump to shoot the electoral moon as a challenger," Donovan said. "And when you're the incumbent, it turns out these things tend to be about you and your record."
Tim Hogan, communications director for Sen. Amy Klobuchar's 2020 presidential bid, said the litany of anti-Biden attacks are "just not believable and scream desperation."
"They have no idea what to do with Joe Biden, so they cycle through a message a minute, and nothing sticks," Hogan said. "It's near impossible to critique an opponent when people are dying and you're the guy directing the botched response to a global pandemic."