At a rally in Erie last month, John Fetterman said he turned down living in the “lieutenant governor governor.” He meant the “lieutenant governor’s mansion,” trying to draw a distinction between himself and his opponent, a celebrity with several multimillion-dollar homes.

In Pittsburgh a week later, Fetterman jumbled up his point about good-paying jobs. “What is wrong with demanding for an easy, safe, kind of their income, a path to a safe place for them to win? Excuse me, to work?” he said.

As Fetterman has returned to the trail, giving candid speeches without notes, he’s been upfront about the lingering speech impacts of his May stroke, insisting his physical and mental health are good, while his opponent, Mehmet Oz, challenges his ability to serve.

“My health now is robust. I’m able to live a normal life,” Fetterman said in his first nationally televised interview on MSNBC. “Driving, going to the grocery store ... it’s just that every now and then, I’m going to miss a word or mush two words together.”

Fetterman and his Senate campaign have said it’s called auditory processing, an effect of his May 13 stroke, along with some word retrieval issues, which they expect to continue to improve. In brief speeches he’s given on the trail, it’s noticeable but not an overwhelming distraction. His crowds, typically supporters, enthusiastically respond to him, and plenty of people have speech problems that don’t indicate cognitive impairment.

As clips of Fetterman’s verbal fumbles have circulated, Oz, a cardiothoracic surgeon who trails slightly in most polls, has amped up pressure on Fetterman to debate. Fetterman said on Wednesday that he will debate Oz sometime in mid-to-late October. His campaign has stressed that he is fully capable of serving as a U.S. senator.

Meanwhile, Oz and his campaign operatives have begun questioning whether Fetterman can be an effective U.S. senator if speech and hearing issues persist. They’ve also insinuated Fetterman’s health issues could be more serious, while sharpening their tone and calling the Democrat a “coward” and “a liar.”

“All the things they’re doing are raising more questions about an issue that didn’t need to be an issue if they were fully transparent about it,” said Barney Keller, a strategist for the Oz campaign. “If he is too sick to debate, then he should just say so, and we would understand, and we think voters would understand.”

Fetterman’s campaign pointed to a recent string of parades, public events, and fund-raisers to dismiss Oz’s attacks.

“Anyone who’s seen John speak knows that while he’s still recovering, he’s more capable of fighting for PA than Dr. Oz will ever be,” spokesperson Joe Calvello said.

The Fetterman campaign was slow to provide details about Fetterman’s health after his stroke. It released a letter from Fetterman’s cardiologist in Pittsburgh in June, which gave the lieutenant governor a good prognosis but also revealed his heart issues dated back to 2017.

None of the doctors who performed the surgery to implant a defibrillator and pacemaker or his current medical team have provided details about the procedure or their prognosis.

Fetterman’s campaign insists it’s been transparent in uncharted waters.

“There’s no playbook for running the biggest race in the country as your candidate recovers from a stroke,” senior campaign adviser Rebecca Katz said.

What is auditory processing disorder?

Sarah Lantz, a speech language pathologist at Magee Rehabilitation, said challenges with communication are extremely common in stroke survivors.

Auditory processing isn’t an issue with hearing, but the way the brain processes words.

Katz said Fetterman does best in one-on-one conversations but has difficulty in situations with several speakers. In Zoom interviews with reporters, the campaign has used closed captioning to make sure he gets the questions. The campaign hasn’t taken any questions from gathered reporters at media events or done news conferences, which can be hectic.

Lantz said patients four months past a stroke, like Fetterman, are still in the acute phase of recovery. She said most recovery happens within six months to a year, but she often works with patients beyond that.

Fetterman goes to speech therapy a few times a week, his campaign said.

Lantz said such sessions could include exercises to help the brain retrieve words and also remedies to use when it can’t — like describing a thought or finding alternate words. Therapists might also work on figuring out what environmental factors have an effect. But no one brain injury is like another.

Lantz stressed that if the issue is solely a lingering language disorder, word stumbles wouldn’t indicate anything about a patient’s intellect.

“People tend to jump to assume that if they hear a person jumble their words or have blips in their speech that means they also have deficits in their problem-solving, reasoning, critical thinking abilities, which is just not necessarily the case,” she said.

Could Fetterman’s stroke impact him in the Senate?

In discussing Fetterman’s challenges, both political sides have painted vastly different pictures of how the Senate operates.

Sen. Pat Toomey on Tuesday called the Senate a place where there’s “intense and sometimes informal, sometimes spontaneous oral communication.” He said based on what he’s seen, Fetterman is not up to that.

Sen. Bob Casey, who endorsed Fetterman and has spent time on the trail with him, said most of the work in Washington is going to hearings, where you may ask a question and get an answer; casting votes; and then attending a lot of one-on-one meetings.

“John will be more than prepared to do that,” Casey said. “Some of the people commenting don’t really understand the work or they have a political ax to grind.”

Several senators have had strokes, two of them — Sen. Chris Van Hollen (D., Md.) and Sen. Ben Ray Luján (D., N.M.) — within the last year.

Wendy Schiller, a Senate historian and professor at Brown University, said the amount of live Senate debate has substantially decreased since the 1990s.

“Thirty years ago, you could argue it would have an effect on his ability to be a senator,” she said. “But the parties have concentrated agenda power so intensely in their own hands that they’ve taken a lot of policy-making power away from committees.”

In a narrowly divided Senate, delivering a pivotal vote will likely be more impactful than delivering an eloquent speech, Schiller said.

How might it impact the race?

In polls, most Pennsylvania voters say Fetterman’s stroke does not have a major effect on their vote. More people said Oz being from New Jersey would have an impact.

Schiller said Oz’s attacks could backfire.

“I think beating up on somebody who’s recovering from something like that gets at the heart of what people over 65 fear, which is that if you get an illness you’re gonna get shoved aside,” she said.

Fetterman has capitalized on the moment and shamed Oz for mocking a stroke survivor.

Brock McCleary, a GOP operative uninvolved in either Senate campaign, said he thinks there’s a double standard compared with scrutiny of President Donald Trump’s health.

“If cognitive function matters with Donald Trump, it’s not unreasonable for it to matter with John Fetterman,” he said.

He dismissed the line of thought that Oz’s strategy could backfire.

“Any candidate in his position would do this. Anything else would be political malpractice.”

In a race that has tightened since the spring, both candidates need to appeal to undecided voters. Whether Oz’s questions about Fetterman’s health resonate remains to be seen.

Fetterman’s base, though, hasn’t shown signs of abandoning him. In interviews with a dozen attendees at his rally in Erie last month, none said they were concerned with Fetterman’s abilities.

Ron Hiles, a 64-year-old retired General Electric worker, said Fetterman’s halting speech didn’t matter, “because what he’s saying, he’s saying the right things,” Hiles said.

“And he speaks from the heart.”