Biden, Trump spin, navigate expectations game ahead of debate: ANALYSIS

President Joe Biden and former President Donald Trump are working to meet vastly different expectations for their performances at Thursday's debate -- expectations that, for each, have been largely set by Republicans.

With enduring voter concerns expressed in polls over Biden's age and mental fitness, but also fueled largely by a robust conservative social media and cable ecosystem, operatives in both parties suggested to ABC News the bar for Biden has been lowered to the point that even a coherent message would exceed expectations.

At the same time, Trump and his allies have emphasized what they tout as the former president's stamina, setting a standard that could prove difficult to exceed.

"I think the Republicans have made the mistake of saying, 'Joe Biden's barely alive and Trump's Mr. Vigor,'" said Peter Giangreco, a Democratic strategist and Barack Obama campaign alum. "They've set those expectations. They've really set Trump up to fail."

Raising questions about Biden's fitness for office has been a cornerstone of GOP strategy, with Trump, Republican lawmakers and allies in the media making unsubstantiated claims about his mental faculties based on verbal mishaps and floating the idea that the president wouldn't live through a second term, including by disseminating deceptively edited video clips of his public appearances.

The Republican messaging has at times veered into conspiratorial waters, with Trump and others suggesting any strong showing by Biden, similar to his energy level in his State of the Union address in March, would be due to performance-enhancing drugs.

"Joe Biden doesn't have a clue. Now we're going to watch. Is anybody going to watch the debate? He's going to be so pumped up," Trump said at a rally last week in Racine, Wisconsin. In Philadelphia on Saturday, he claimed Biden would be "jacked up" by getting a shot "a little before debate time."

The White House and Democratic allies have ridiculed the drug-use allegations but also have been relatively conservative in public about how strongly Biden will perform on Thursday.

On the flip side, Republicans have elevated Trump as a paragon of vitality, citing his numerous media interviews and long speeches at rallies, which themselves are often pockmarked with factual errors and flubs.

"President Trump takes on numerous tough interviews every single week and delivers lengthy rally speeches while standing, demonstrating elite stamina," Trump senior advisor Jason Miller told ABC News.

That kind of rhetoric has some Republicans wondering whether they've boxed themselves in on the expectations game.

"The Republicans, and particularly the conservative media, have not done any favors here by portraying Biden as meandering, stumbling, can barely put a sentence together, because they've just lowered his expectations to the floor. All he's going to have to do is basically show up and sound halfway decent, and he will meet the expectations he has," said GOP strategist David Kochel, who advised Jeb Bush's 2016 campaign.

Trump appeared to try to bump expectations for Biden, saying on a podcast on Thursday that he "will be somebody who will be a worthy debater" and that "I don't want to underestimate him." He and his campaign have also cast CNN moderators Dana Bash and Jake Tapper as out to get him, another apparent attempt to influence the expectations game.

Yet, when asked if Republicans could effectively raise Biden's expectations before Thursday, Kochel replied, "It's too late for that."

"I think there should have been a meeting or an agreement that you're gonna have Biden's expectations a lot higher, but it is what it is," he said. "They've been driving this doddering old narrative for a while."

Democrats, meanwhile, are hopeful that Biden could emerge from Thursday with a boost, a departure from a level of hand-wringing that has become cliché in political circles.

"Anything short of Biden forgetting his first name or having a major physical, mental, psychological breakdown on stage means Biden is likely to, at least from the expectations game, walk away the winner. That's how poorly the Republicans have managed expectations," said one Democratic pollster.

Strategists of both parties said exceeding expectations and having a strong debate could be a rare opportunity for both candidates to change voter perceptions of them and try to alter stubbornly stable polling.

Trump is anticipated to light into Biden over the economy and the border, two issues polls show are top voter concerns, with Republicans a contrast, posed effectively, could help supercharge Trump's campaign -- particularly if viewers also see a more visual contrast in verve between the two candidates on stage.

"Voters want him to be a disruptor, whether it's in performance, whether it's in rhetoric, or whether it's in results, and all he has to do is point to his first term as president as being disruptive with a model of economic success, and that's what he has to do. That's what wins this debate," said one former Trump campaign official who remains in touch with the former president's current team.

Still, some Republicans wanted a disruptor with a milder temperament on stage, worrying that attempts to shout down Biden would rub voters the wrong way.

"Good performance for Trump is not to be over aggressive toward Biden," one attendee of a Trump fundraiser in Louisiana told ABC News when leaving the event on Monday. "Let Biden run."

For Biden, Democratic strategists said, a strong performance on such a large stage could help tamp down worries over his age -- a voter concern perceived to be a major obstacle in Biden's path to reelection.

"I see the debates as a real opportunity for him to demonstrate that he has what it takes to do the job of president effectively and assuage a lot of those concerns that are currently holding back a lot of Democratic-leaning voters from supporting him," said one source familiar with the Biden campaign's strategy.

Still, it's unclear precisely how much the narrative around Biden's age could be tamped down.

While Biden delivered what was widely regarded as a strong State of the Union in March -- leading Democrats to cheer the demise of talk about Biden's fitness -- their concern continued after only a brief reprieve.

The source familiar with the Biden campaign's strategy said focus-group data suggest voters view an unscripted debate as different from a State of the Union. But it remains to be seen how much a clear debate win would supercharge Biden's campaign while polls show voters trust Trump more on top issues.

"That narrative is very ingrained already, and the biggest challenge for the for the Biden campaign is that their entire campaign is based on telling people 'what you see with your own eyes, what you feel in your own pocketbook, what you see happening going on at the southern border isn't real, believe me,'" said former Trump campaign official Marc Lotter. "That's a difficult position for any campaign to be in."

Still, falling short of expectations could become a significant stumbling block for either candidate.

Operatives said an "unhinged" Trump who focuses more on Biden's family and voter fraud could remind swing voters who backed Biden in 2020 why they first rejected the former president, while a faltering performance by the president could inflict one of the worst kinds of damage a campaign could suffer -- reinforcing a preexisting idea.

"If Trump seems unhinged, Biden's campaign will gain a lot of momentum. He'll quickly excite his base, and you will see independents shift to him. If Biden appears too old, doesn't seem in control, doesn't seem able to do the job, that will depress his base's excitement, it will scare independent voters and really energize the Republicans in a way that will make it hard for his campaign to recover," said Alex Conant, who worked on the 2016 presidential campaign of Florida GOP Sen. Marco Rubio, whose own White House ambitions were dashed partially by a poor primary debate performance.

"Both candidates," Conant said, "have a lot on the line."

Soo Rin Kim contributed to this report.