John Fetterman, the Democratic candidate whose health has been mocked by his Republican opponent, Mehmet Oz, during a rancorous race for Pennsylvania’s US Senate seat, has admitted the stroke he suffered in May “changes everything” about his life.

In a televised interview with NBC, in which he used a closed captioning machine to be able to read the questions put to him, he insisted his disability was temporary, and that in January “I’m going [to] be much better – and Dr Oz is still going to be a fraud”.

His comments are the latest chapter in a tightening race that could decide control of the Senate.

Fetterman and his opponent, whose career as a celebrity television doctor drew claims of quackery for allegedly fake diet pills and dubious Covid cures, have lobbed acrimony at each other throughout the campaign. Earlier this month, Fetterman seized on allegations of animal cruelty against Oz from his time as a researcher at Columbia University.

In the NBC interview, Fetterman struggled to pronounce some words and had difficulty finding others. He conceded the stroke had affected his auditory processing and speech skills, which he deliberately highlighted after initially struggling to correctly express the word “empathetic”, also pronouncing it “emphetic”.

“That’s an example,” he said. “I always thought I was empathetic before the stroke. I now really understand much more the kind of challenges Americans have day in, day out.”

Asked by interviewer Dasha Burns how the stroke affected his own day-to-day life, Fetterman said: “It changes everything. Everything about it has changed.

“I sometimes will hear things in a way that’s not perfectly clear. So I use captioning so I’m able to see what you’re saying.

“And every now and then I’ll miss a word. Or sometimes I’ll maybe mush two words together. But as long as I have captioning, I’m able to understand exactly what’s being asked.”

Fetterman, Pennsylvania’s lieutenant governor, recommenced public appearances in August after the stroke. He denied it would affect his ability to serve as a senator: “I don’t think it’s going to have an impact. I feel like I’m gonna get better and better, every day.”

Oz’s campaign staff accused Fetterman of “hiding” when he dropped out of a debate in the summer. Following the Republican’s offer that “at any point John Fetterman can raise his hand and say bathroom break. We will pay for any additional medical personnel [he] might need to have on standby,” Fetterman retorted that “Dr Oz’s team … think it is funny to mock a stroke survivor.”

Fetterman told NBC: “You can’t be any more transparent than standing up on a stage with 3,000 people and having a speech without a teleprompter and just putting everything and yourself out there like that. That’s as transparent as everyone in Pennsylvania can see.”

Fetterman also attacked Oz over abortion, and defended himself against accusations that he was “soft on crime”.

“If you’re going to be our next senator, you have to give the answer,” Fetterman said, referring to Oz’s wavering stance on abortion. “[Women] believe their choice belongs with them, and not with Dr Oz or the Republicans.”

Recent polling aggregated by Real Clear Politics shows Fetterman maintaining a slender lead over Oz, down from double digits earlier in the year, with less than four weeks until election day.

Oz has focused on Fetterman’s positions on crime, accusing his opponent of wanting to release one-third of Pennsylvania’s prisoners. Some of Oz’s attacks have been labeled “misleading” by factcheck.org, including a claim that Fetterman wanted to legalize heroin.

“I believe in redemption,” Fetterman told NBC, citing the Oscar-nominated movie film Shawshank Redemption to explain his stance.

“If you, at the end of the movie, would vote to have Morgan Freeman’s character die in prison, then that’s really the choice,” he said. “I haven’t met a single person that’s said, ‘Yeah, Morgan Freeman should die in prison.’

“It’s all a choice on redemption, and giving somebody a chance to not die in prison that is not of any danger to the public whatsoever.”