Republicans want you to think Biden's on drugs at the debate because they've set expectations too low for him

• Republicans regularly portray Joe Biden as feeble and unable to serve as president.
• Ahead of his debate with Trump, they're changing course — even saying he'll be on drugs.
• It's a recognition that they've set expectations too low for Biden, and it could backfire.

Day in and day out, Republicans portray Joe Biden as a man who's too old and enfeebled to carry out the duties of the presidency.

It's probably their most potent attack, given that most Americans are concerned about his age. At 81, Biden is the oldest person to ever serve as president, and there's no denying that he shows it at times.

But now, ahead of a high-stakes debate with Donald Trump on Thursday, some Republicans are adding a twist to that narrative: Biden may show up under the influence of drugs.

The most outspoken of the bunch is Rep. Ronny Jackson, a staunch Trump ally who previously served as White House Physician from 2013 to 2018: The Texas Republican sent a letter to Biden demanding that he take a drug test ahead of the debate.

There's also the more anodyne version of the theory, pushed by Republicans like Rep. Eric Burlison of Missouri, who speculated that Biden's advisors were "going to jack him up on Mountain Dew."

Why are Republicans bothering to talk about this at all?

It may be because they realize their portrayal of Biden as enfeebled may only work in the president's favor at the debate.

It all goes back to the State of the Union

"A little before debate time, he gets a shot in the ass," Trump said at a rally in Philadelphia on Saturday. "He'll come out all jacked up, right? All jacked up."

"I'm sure he'll be prepared," Trump later added. "Whatever happened to all that cocaine that was missing a month ago from the White House?"

This sort of thing isn't new for Trump. In 2016, he suggested that he and Hillary Clinton should submit themselves to a drug test, and in 2020, he suggested that Biden was on drugs when he debated his Democratic primary opponents.

What's new is the embrace of that theory by rank-and-file Republicans, most of whom seem to have been taken aback by Biden's relatively strong performance at the State of the Union address in March.

"He was very different in the State of the Union than he has been for the last three and a half years in public," Jackson told Business Insider.

"I remember walking into the State of the Union and thinking, 'We're going to see sleepy Joe,' and we saw jacked up on Mountain Dew Joe,'" Burlison told Business Insider. "I think that he's going to be attentive, alert, because it's going to be game on."

When Biden spoke to Congress, he had been facing one of the worst months of his campaign. Special Counsel Robert Hur's report had characterized the president as an aging man with a poor memory, and liberal pundits were openly discussing the merits of replacing him.

Biden managed to reset the narrative with a State of the Union address that was energetic and highly political. While it didn't result in a lasting lead for the president, it gave him a modest bump in polling.

The president has been in debate prep for days, and he's likely looking to snag a similar opportunity on Thursday.

Neither Burlison nor Jackson went so far as to admit that they're playing an expectations game with Biden, but both men acknowledged that it's an important factor.

"Probably, the expectation has been set too low," said Jackson. The Texas congressman predicted that Biden would either be "sleepy" or "jacked up" at the debate, but acknowledged that the president could land somewhere in the middle. "If that happens, I mean, then it's a win for him, right?"

"I don't think we ought to underestimate [Biden]," said Burlison. "Trump's team should be fully prepared, and not be planning for sleepy Joe."