PITTSBURGH — John Fetterman, the liberal lieutenant governor of Pennsylvania who gained his state’s Democratic nomination for Senate on Tuesday, gave the impression to be cruising into what’s shaping up as one of the intently watched basic elections within the nation this fall. Then a stroke upended his plans.

Mr. Fetterman, the 6-foot-8, hoodie-wearing former mayor of Braddock, Pa., was not a favourite of the occasion institution, however he electrified some progressive voters and a broader slice of the Democratic voters that embraced his blunt-spoken, accessible style and welcomed his pledges to combat aggressively for occasion priorities in Washington.

“I’m simply doing my factor,” he mentioned in an interview final week. “I’m only a dude that reveals up and simply talks about what I consider in, you understand?”

After canceling marketing campaign occasions on Friday, Saturday and Sunday, Mr. Fetterman, 52, announced that he had had a stroke, was recovering and had not suffered any cognitive harm.

He was nonetheless within the hospital on Tuesday, when his marketing campaign introduced that he would endure “a regular process to implant a pacemaker with a defibrillator,” including, “It needs to be a brief process that may assist defend his coronary heart and deal with the underlying reason for his stroke.”

It was unclear when he would have the ability to resume campaigning.

The well being scare carried ramifications far past Pennsylvania. Democrats maintain a majority within the Senate solely by advantage of Vice President Kamala Harris’s tiebreaking vote. The occasion’s vulnerability had already been highlighted when Senator Ben Ray Luján of New Mexico suffered a stroke in January.

It additionally appeared jarring given Mr. Fetterman’s vigorous public picture; he typically was dressed as if he’d simply left the fitness center.

“He might not seem like a Senate candidate for New York or California, however he’s simply fantastic for Pennsylvania,” mentioned Ed Rendell, a Democratic former governor of the state. “He’s a really plausible candidate for the working class.”

Mr. Fetterman, who holds a level from the Harvard Kennedy College, served for 13 years because the mayor of Braddock, the place he attracted consideration for his efforts to revitalize a struggling metal city — and scrutiny over a 2013 episode through which he brandished a shotgun to cease an unarmed Black jogger, telling the police he had heard gunshots.

He ran unsuccessfully for the Senate in 2016 however gained an enthusiastic following, and went on to defeat an incumbent to win his occasion’s nomination for lieutenant governor in 2018. In that function, he maintained an lively presence across the state, constructing title recognition that performed an essential function in his major victory.

“He spent lots of time in communities all through the state,” mentioned Senator Bob Casey of Pennsylvania, who didn’t take sides within the major. “That’s one thing he’s been capable of construct on.”

Mr. Fetterman additionally made a reputation for himself in nationwide progressive circles, receiving the endorsement of Senator Bernie Sanders of Vermont in 2018 after he backed Mr. Sanders’s 2016 presidential major bid. And he gained fresh prominence with a broader vary of voters as a cable-television fixture when Pennsylvania’s 2020 votes have been being counted.

A number of months later, he entered the Senate major, the first main Democratic candidate to leap into the race, and cemented an amazing fund-raising benefit over his nearest rivals.

Mr. Fetterman campaigned on points like elevating the minimal wage, selling felony justice reform and supporting voting rights, abortion rights and protections for L.G.B.T.Q. individuals.

However he attracted simply as a lot consideration for his fashion, and a few noticed him as expert at connecting with blue-collar voters. He favored basketball shorts and sweatshirts over button-downs and khakis and spent vital time campaigning in rural, working-class counties that had overwhelmingly voted for former President Donald J. Trump, hoping to enhance Democratic margins in these areas.

Mr. Fetterman has repeatedly described himself as a progressive up to now, however within the Senate race he didn’t search the left-wing mantle. He rejected a suggestion final week that he would be a part of the “Squad,” a gaggle of left-wing members of Congress, ought to he win.

Republicans and a few Democrats, nevertheless, consider that he could also be susceptible to criticism that he’s too far to the left for one of the intently divided states within the nation, and particularly for its extra centrist suburbs, which have been very important to current Democratic beneficial properties within the state.

“It’s good that Fetterman goes to those areas the place Democrats have achieved poorly in these Republican counties, however I believe his greater problem goes to be these suburban communities,” mentioned former Consultant Charlie Dent, a Pennsylvania Republican who said he had voted for President Biden.

Mr. Dent warned that Mr. Fetterman is seen by some as a “Bernie Sanders Democrat.”

The lieutenant governor lives in Braddock together with his three kids and his spouse, Gisele Barreto Fetterman, the second woman of Pennsylvania, who has embraced the acronym “SLOP” and who, like Mr. Fetterman, has an lively social media presence.

She insisted that he get checked out after feeling unwell on Friday, the Fettermans mentioned.

His marketing campaign mentioned Monday that Mr. Fetterman had been “once more evaluated by the neurologist who as soon as once more reiterated that John will make a full restoration.”