"Athletes, they make them take a drug test," Trump said at a Portsmouth, New Hampshire, rally. "We should take a drug test prior to the debate because I don't know what's going on with her. But at the beginning of her last debate, she was all pumped up at the beginning. And at the end … she could barely reach her car."
"I'm willing to do it," he added.
Clinton is not campaigning this weekend in order to prepare for the third and final debate Wednesday, an aide told NBC News.
Trump tweeted before the New Hampshire rally that he would speak about "the massive drug problem there, and all over the country." The state is in the midst of a drug overdose crisis propelled by the heroin epidemic.
Tweet: Landing in New Hampshire soon to talk about the massive drug problem there, and all over the country.
After slamming the latest Clinton emails released by WikiLeaks as proof that "the media collaborates and conspires directly with the Clinton campaign," Trump turned his attention to heroin and other drugs "that are poisoning our youth."
"You're the ones who really showed me the gravity of the problem of drugs pouring in, mostly from the southern border," Trump told the crowd in Portsmouth, doubling down on his promise to build a wall along the U.S.-Mexico border.
He also outlined his plan to help Americans struggling with drug addiction by expanding access to treatment centers and giving caregivers access to Narcan — a life-saving opiate antidote that can be administered following an overdose.
And he vowed to hold U.S. Department of Veterans Affairs more accountable, so vets got the proper care.
"We have to solve this crisis and we will," Trump said.
The scripted comments came a day after the Republican presidential nominee ditched his broken teleprompters while speaking in North Carolina — capping off an unpredictable several days in which Trump was forced to defend himself against a barrage of allegations of inappropriate advances toward women, some dating back decades.
Trump has vehemently denied the allegations made by the eight women and went so far Friday to imply the accusers were too unattractive for his standards. He claims he's the victim of a left-wing conspiracy and that the media is colluding with Clinton to smear him.
He prolonged that attack on the media Saturday, pointing to the leaked Clinton emails.
"They show how the media collaborates and conspires directly with the Clinton campaign," Trump said. "The election is being rigged by corrupt media pushing false allegations and outright lies in an effort to elect her president."
Clinton campaign manager Robby Mook struck back Saturday, and said the American electoral system " is free, fair and open" in response to Trump's comments.
"Participation in the system — and particularly voting — should be encouraged, not dismissed or undermined because a candidate is afraid he's going to lose. This election will have record turnout, because voters see through Donald Trump's shameful attempts to undermine an election weeks before it happens," Mook said in a statement.