For months, President Donald Trump has taken shot after shot after shot at Joe Biden over his mental fitness. On Tuesday, that line of attack will be put on trial at the first presidential debate, giving Biden his best opportunity yet to, as he has said, "compare my cognitive capability to the cognitive capability of the man I'm running against."
While Biden has suffered from some verbal slip-ups along the campaign trail as well as a slate of primary debates that were somewhat of a mixed-bag for the nominee, what political observers described as the "low expectations" being set by Trump should play to the former vice president's advantage in Cleveland.
"The ironic thing about the constant hyperbolic attacks by the president and his campaign on the former vice president's mental health or physical health is they've created a situation where if he doesn't pee himself — like Bradley Cooper in 'A Star Is Born' — he will have exceeded expectations," said Michael Steel, who helped prepare Paul Ryan for his 2012 vice presidential debate against Biden.
Alan Schroeder, a Northeastern University professor and expert on presidential debates, said Trump's low-balling of Biden's abilities "jumped out at me early on" as curious, saying he couldn't think of any similar example from past presidential cycles.
"I think they looked at the primary debates...saw that Biden was not great in those and figured that's the guy that's going to show up in September," Schroeder told NBC News. "But there's a huge difference between primary debates, where you have 10 people on the stage, and a one-on-one debate."
Biden has spent the lead-up to the debate in traditional preparation. Trump, on the other hand, has eschewed that, telling aides he's not concerned about debating Biden because he thinks the former vice president will probably have a bad gaffe.
Trump has repeatedly claimed Biden is unaware of his surroundings, cannot communicate without a teleprompter and calls him "sleepy Joe." Allies have promoted misleading or false videos about Biden's stamina, mental health and teleprompter usage. The Trump campaign has spent millions on ads arguing Biden is "diminished" and "slipping."
Biden has sought to flip the attacks back onto Trump, who has suffered verbal missteps of his own. And Biden has pointed to physical issues, like when Trump awkwardly descended down a ramp after speaking at West Point this year.
"Look at how he steps, and look at how I step," Biden told WHTM. "Watch how I run up ramps and he stumbles down ramps."
Former Rep. Carlos Curbelo, R-Fla., said he does not see the advantage of Trump's pre-debate attacks on Biden's mental abilities.
"If (Trump) was a Ronald Reagan or Bill Clinton or another great communicator, I would understand this theme," Curbelo said. "But Donald Trump is not always the most coherent and rarely eloquent in his discourse."
Polling on the subject is mixed. A July Monmouth University survey found more voters believed Biden, 77, has the mental and physical stamina to be president than felt so about Trump, 74. Earlier this month, a CNBC/Change Research poll of several swing states showed a small majority of voters felt both Biden and Trump are not mentally fit to be president.
Sen. Chris Van Hollen, D-Md., who played Ryan in Biden's 2012 debate prep, told NBC News that if the president attacks Biden's cognitive abilities Tuesday, it "will show Trump to be the dishonest bullying person that he is."
Biden "needs to focus on what he will do for the country," Van Hollen said, adding, "When Donald Trump tries to get down in the mud, as he does every day, let him sink in it."
As the debate has neared, Trump and his campaign have changed their tune. During a rally last week in Ohio, Trump said Biden has "been doing this for 47 years. I've been doing it for 3 1/2 years, so he should be able to beat me," though he said in the same event that Biden was "shot," "sleepy" and "the worst presidential candidate in the history of politics."
"Joe Biden has been a Washington politician for 47 years, debated very well twice while running for vice president and just came through 11 debates in the Democrat primaries where he defeated two dozen challengers," Trump campaign communications director Tim Murtaugh said. "Joe Biden is a master debater who knows what he’s doing."
That tone is more in line with traditional pre-debate messaging — raising expectations for the opponent and keeping expectations low for your own candidate.
Biden advisers and allies have taken that approach. As one Biden ally told NBC News, Trump's "presidency has been so controversial and divisive that he's effectively been in a debate on most days since he took office," saying that will work to Trump's benefit.
Speaking with MSNBC's Stephanie Ruhle last week, Biden predicted Trump's strategy for the debate will "be straight attack."
"They're going to be mostly personal," Biden said. "That’s the only thing he knows how to do. He doesn’t know how to debate the facts because he’s not that smart. He doesn’t know that many facts."
Ted Olson, the former U.S. solicitor general who played Biden in Ryan's 2012 debate prep, said the former vice president needs to be "crisp ... concise and direct" in his answers. He said Biden should take care not to "wander off the subject matter. That's going to be very difficult under the circumstance with this particular opponent."
"You can't drift because that's what old people do, and I'm older than both of them, so I can say this," added Olson, 80. "Sometimes these politicians never want to stop talking, and that's not going to look good for a person of a certain age."
Olson said a good example of how Biden should tackle this topic comes from Reagan who, when asked in a 1984 debate if he was too old to be president, cracked a memorable joke: "I am not going to exploit, for political purposes, my opponent's youth and inexperience."
"It was a perfect answer because it brushed it away," Olson said. "He didn't take it seriously. He didn't act like he was threatened by it and boom! It was over."