Pennsylvania Lieutenant Governor John Fetterman is on his way to “full recovery” after suffering a stroke days before the US state's primary election, his campaign said in a statement.
The revelation created uncertainty over Mr Fetterman's candidacy only two days before voters were scheduled to head to the polls.
Mr Fetterman will remain in hospital through the day of the primary and skip a scheduled rally on Tuesday night in Pittsburgh, US media outlets reported.
“Fortunately, my wife, Gisele, spotted the symptoms and got me to the hospital within minutes,” Mr Fetterman said.
In a 16-second video posted on Twitter, Mr Fetterman said he “just wasn’t feeling very well” on Friday and that his wife insisted he go to hospital before an appearance at Millersville University.
Mr Fetterman's stroke was “caused by a clot from my heart being in an A-fib rhythm for too long”, he said. The doctors “quickly and completely” removed the clot.
“The good news is I'm feeling much better and the doctors tell me I didn't suffer any cognitive damage,” he said.
“The doctors have assured me that I'll be able to get back on the trail, but first I need to take a minute, get some rest and recover.”
Mr Fetterman pledged to continue his campaign despite the medical setback.
“Our campaign isn’t slowing down one bit and we are still on track to win this primary on Tuesday and flip this Senate seat in November,” he said.
Democrats see the election to replace retiring Pat Toomey as one of their best chances to pick up a seat in the Senate, where the party holds a razor-thin majority. Voters will decide their parties' nominees on Tuesday.
As of Monday, Mr Fetterman holds a sizeable advantage over his Democratic rivals heading into Tuesday's primary, polling data compiled by RealClearPolitics show.
The Republican primary features celebrity heart surgeon Mehmet Oz, former hedge fund executive David McCormick and conservative commentator Kathy Barnette, among others.
The Associated Press contributed to this report