President Donald Trump demanded on Sunday that his Democratic rival Joe Biden take a drug test for their first debate, which will bring them face to face for the first time in the volatile US presidential campaign.
Tuesday's clash, coming as Mr Biden leads the charge against Mr Trump's bid to install conservative Amy Coney Barrett in the late Ruth Bader Ginsburg's lifetime seat on the Supreme Court, will thrust the nail-biting contest into a fierce new stage.
Mr Trump, lagging in the polls, taunted Mr Biden on Sunday with the fresh salvo on his mental acuity.
"I will be strongly demanding a Drug Test of Sleepy Joe Biden prior to, or after, the Debate on Tuesday night," he tweeted, saying he would take one also. "His Debate performances have been record setting uneven, to put it mildly. Only drugs could have caused this discrepancy???"
The president offered no evidence to support his insinuation, and recently-completed negotiations between the Mr Biden and Mr Trump camps over debate conditions reportedly made no mention of any drug test.
When asked by reporters about the demand Sunday, Mr Biden laughed before declining to comment.
Both septuagenarians are prone to blunders and gaffes when speaking, but the 74-year-old Mr Trump has repeatedly depicted the 77-year-old Mr Biden as mentally unfit.
Mr Biden has shrugged off such accusations. On Saturday he said he expects "personal attacks and lies" from the president, likening Mr Trump to Nazi propaganda chief Joseph Goebbels.
People walk east on West Sixth Street in support of Democratic presidential candidate Joe Biden and running mate Kamala Harris in Erie, Pennsylvania. Source: Erie Times-News
The former vice president has until recently stayed close to his Delaware home due to the challenges of campaigning in person safely during a pandemic.
Mr Trump, meanwhile, has been flouting his own government's social distancing guidelines to criss-cross battleground states, speaking frequently at mass rallies where participants are often tightly packed with few masks in sight.
High stakes
Mr Trump sees his nomination of Barrett to the Supreme Court, potentially tilting the court to the right for years, as a fundamental boost to his troubled campaign.
He told Fox & Friends Sunday the Senate will "easily" confirm Ms Barrett before the election, despite furious Democratic opposition.
But Mr Biden hit back, accusing Mr Trump of rushing Ms Barrett's nomination in order to launch a new assault on health care.
The president and the Republican-held Senate "see an opportunity to overturn the Affordable Care Act on their way out the door," Mr Biden told reporters in Wilmington, Delaware.
He again urged the Senate to delay the confirmation until after the election, noting that early voting had already begun.
"Never before in our nation’s history has a Supreme Court justice been nominated and installed while a presidential election is already underway," he said.
Barring a huge surprise, Republican senators, who have 53 out of 100 votes in the upper house of Congress, are expected to confirm Ms Barrett.
Democratic presidential candidate former Vice President Joe Biden gives a speech on the Supreme Court at The Queen Theatre in Wilmington, Delaware. Source: AP
Confronting Mr Trump
The TV debate will be a wild card.
Mr Trump needs to break through the 200,000 coronavirus deaths, the long-lasting economic fallout, and the widespread fatigue at the constant upheaval roiling his administration.
He sees himself as a tough guy and has huge confidence in his prowess on stage.
Yet unlike the fawning treatment he enjoys during his weekly call-ins to Fox News or the adoring atmosphere at rallies, he'll find himself facing a determined rival painting him as "toxic" in front of the entire country.
"When Joe Biden walks onto the debate stage, it will be the first moment in four years where an American has the opportunity to confront Donald Trump for what he's done," Steve Schmidt, a Republican strategist turned outspoken Trump opponent, said on MSNBC.
Frontrunner Joe Biden mainly needs just to keep steady against a man many call a master provocateur.
"There is virtually no doubt that Mr Trump will try to bait him," David Barker, director of the Centre for Congressional and Presidential Studies at American University, said.
Who's more ready?
Mr Biden, though, survived the Democratic primary debates earlier this year and has made a string of generally well-received speeches on the campaign trail.
And while Mr Trump often takes questions from groups of journalists, it's rare that he'll do the more risky one-on-one televised session with a tough interviewer. Neither has he had to debate an opponent face-to-face since Clinton in 2016.
"Normally, that first debate is the toughest for the incumbent," said Aaron Kall, director of debate at the University of Michigan.
The debate moderator, Fox News host Chris Wallace, has set topics ranging across the Supreme Court, the pandemic and economic disasters, racism and the integrity of the election.
But whether Mr Wallace can keep the two men on topic remains to be seen.
