Lt. Gov. John Fetterman of Pennsylvania, the front-runner for his state’s Democratic Senate nomination, said on Sunday that he had had a stroke on Friday and was recovering.

“I had a stroke that was caused by a clot from my heart being in an A-fib rhythm for too long,” he said in a statement. “The amazing doctors here were able to quickly and completely remove the clot, reversing the stroke, they got my heart under control as well.”

The incident has kept him off the campaign trail for the final weekend before Tuesday’s primary election in one of the nation’s most closely watched Senate contests. It was unclear when he would return to in-person campaigning.

“The good news is I’m feeling much better, and the doctors tell me I didn’t suffer any cognitive damage,” he said in the statement from Penn Medicine Lancaster General Hospital. “I’m well on my way to a full recovery.”

“They’re keeping me here for now for observation, but I should be out of here sometime soon,” he added.

Mr. Fetterman had been scheduled to host a meet-and-greet in Lancaster County, Pa., on Friday morning, but his spokesman, Joe Calvello, said at the time that the team decided to cancel the event because “John was not feeling well this morning so we are taking the necessary precautions.”

The campaign canceled events across the state on Friday evening, Saturday morning and again on Sunday, but gave scant information about the state of Mr. Fetterman’s health over the weekend.

The development upended his ability to engage voters in-person during the most intense stretch of the race. Still, he has been leading his main Democratic rival, Representative Conor Lamb, by double digits in sparse public polling.

Mr. Fetterman’s blunt-spoken liberal politics and penchant for wearing shorts and hoodies at public events appear to have resonated with much of the Democratic base.

“If somebody thinks I’m smarter if I’m in a suit, so be it,” Mr. Fetterman said in an interview on Thursday at the event in York, his hometown. “I would rather have people know what they’re getting and this is who I am.”