Since returning to the campaign trail last month after a mid-May stroke, Pennsylvania Lt. Gov. John Fetterman, the Democrat vying for the state's open Senate seat, sometimes speaks haltingly to voters -- pausing in the middle of sentences and slurring his words.
Otherwise, he has said, he has "no physical limits" and no issues with memory or language comprehension. In an interview on MSNBC last week, Fetterman, who works with a speech therapist, said he was "expecting to have a full recovery over the next several months."
But Republicans have seized on his public appearances and his post-stroke behavior to suggest that he is not fit to serve in the Senate, a claim outside medical experts reject as reductive.
"It's just not possible to be an effective senator if you cannot communicate," retiring Republican Sen. Pat Toomey, whose seat Fetterman hopes to fill, said Tuesday at a press conference with Dr. Mehmet Oz, the GOP nominee and Fetterman's opponent.
Rick Santorum, a former Republican senator from Pennsylvania, was even more blunt in his criticism last week on Newsmax: "John Fetterman is simply not capable of doing this job. He's hiding in his basement, he's not able to talk, he's not able to process."
The scrutiny of and questions about Fetterman's health underscores the stakes of his race against Oz, which could decide who controls Congress' upper chamber next year. Politicians suffering health challenges mid-campaign -- when they would normally be stumping for voters, night and day -- is also relatively rare, and Fetterman's team has been careful of overexposing him while he recovers.
His aides did not respond to requests to make his medical team available for this story. He has, however, previously responded directly to the GOP jabs at his recovery: "I know politics can be nasty, but even then, I could *never* imagine ridiculing someone for their health challenges," he tweeted in August.
"Anyone who's seen John speak knows that while he's still recovering, he's more capable of fighting for [Pennsylvania] than Dr. Oz will ever be," a spokesman said earlier this week.
His campaign has said his stroke was the result of a condition called atrial fibrillation, or irregular heart rhythm, which led to a clot; he subsequently had a pacemaker and defibrillator implanted.
The attacks on him increased as he remained mum on debating Oz, who has pushed to share a stage. Last week, Fetterman declined an invitation from KDKA, a Pittsburgh station, to participate in a debate that would have taken place on Tuesday.
"John Fetterman is either healthy and he is dodging the debates because he does not want to answer for his radical left positions, or he's too sick to participate in the debate," Oz said in the news conference with Toomey, where the two men spoke in front of photographs of debates in previous Senate cycles.
Fetterman then told Politico on Wednesday that he would debate Oz once. In response, an Oz spokeswoman accused Fetterman in a statement of still not being forthcoming on details about the time, place and the topics.
"It was just simply only ever been about addressing some of the lingering issues of the stroke, the auditory processing, and we're going to be able to work that out," Fetterman told Politico.
Outside medical experts said stroke victims' speech difficulties are not indicative of their cognitive abilities at work.
"You certainly should not conflate language troubles with cognitive trouble," John Krakauer, director of the Johns Hopkins Center for the Study of Motor Learning and Brain Repair, told ABC News in an interview. "That's just being mean. It's not scientifically valid. It would be like saying that a stutterer has a cognitive problem."
ABC News spoke with several neurologists in general terms about stroke recovery. None of the experts interviewed have treated Fetterman or reviewed his medical history.
"Let's say you have a little tiny stroke in the part of your brain that controls your right arm," suggested Robert Friedlander, Chair of the Department of Neurological Surgery at the University of Pittsburgh Medical Center. "Your right arm is not going to move, but you're still thinking as you did before."
"You can impact the speech part of the brain [and] might not sound the way you did before the stroke, but the cognitive component could be preserved," added Friedlander, who said that, in some cases, language and cognition could both be affected.
If elected, Fetterman wouldn't be the first stroke victim in the Senate. For example, both Ben Ray Luján, D-N.M., and Chris Van Hollen, D-Md., suffered strokes earlier this year and have both returned to work. (Luján told ABC News in an interview in May that his stroke left him "wobbly" and a "little weak on the left," but without any motor movement or voice issues.)
Fetterman also wouldn't be the first politician to have a health scare while running for office. In late 2019, Sen. Bernie Sanders suffered a heart attack while seeking the Democratic nomination for president. Sanders was hospitalized but quickly returned to the trail.
"Everyone who experiences a stroke will have their own unique recovery process, which is why the only people who can judge fitness for work are the individual's treating physicians," said Dr. Leah Croll, stroke neurologist and assistant professor of neurology at the Lewis Katz School of Medicine at Temple University.
After an earlier period of well wishes and relative silence on Fetterman's health, the Oz campaign has made his stroke a part of its campaign -- sometimes in sharply personal terms. Last month, an aide, Rachel Tripp, was quoted asserting that if Fetterman "had ever eaten a vegetable in his life, then maybe he wouldn't have had a major stroke and wouldn't be in the position of having to lie about it constantly."
In a recent statement, the Oz campaign said that it would "pay for any additional medical personnel he might need to have on standby" during a debate.
"I offered John Fetterman numerous opportunities to explain to me how I can make it easier for him to debate, but at this point, since he's given numerous reasons for not showing up, including the fact he didn't have time in his schedule, I'm of the opinion that he's hiding his radical views," Oz said on Fox News in August.
Krakauer, who overlapped with Oz at Columbia University as a medical student but has no relationship with the GOP Senate candidate, told ABC News that stroke victims tend to fatigue when speaking for long periods of time.
"Your best level of performance can drop over time," he said. "A half an hour debate, an hour debate, over and over again is a lot to expect someone with aphasia [language difficulties from brain damage] to do. But that doesn't mean they're not cognitively capable."
Some Democratic voters told ABC News they hope Fetterman debates Oz but insist they're not concerned.
"People have illnesses all the time, but I think he got the right care," said Geraldine Eckert, from Mercer County, who attended a recent Fetterman event. "I'm not worried about John Fetterman's health."