Freshman Pennsylvania Sen. John Fetterman was hospitalized late Wednesday night after experiencing a bout of lightheadedness while at a Democratic retreat, according to his office.

The senator is in "good spirits" and has remained in contact with his family and staff, Joe Calvello, Fetterman's director of communications, said in a statement.

While initial tests did not show signs of a stroke, doctors are continuing to run tests, and Fetterman was being kept overnight "for observation," Calvello added.

Notably, Fetterman, 53, suffered a stroke just days before his 2022 Democratic primary, setting the stage for a recurring theme during his run for the hotly contested Senate seat. Fetterman went on to win in the general election, defeating Trump-endorsed Republican foe Mehmet Oz in November.

Fetterman's stroke prompted the implantation of a pacemaker and defibrillator, and he said he had previously been diagnosed with atrial fibrillation -- an irregular heart rhythm that can cause blood-flow issues.

The recovery from the May 2022 "near-death" stroke has been ongoing and public, with no better example than Fetterman's performance in a televised debate with Oz in which he fumbled his words and struggled to string together sentences.

The performance became a touchstone for Republicans who argued Fetterman would be unable to perform his duties as a senator, while Democrats largely rallied around the former lieutenant governor and praised him for his bravery.

In an Associated Press profile after his victory, Fetterman was described as having an auditory processing disorder, which can affect a person's ability to understand speech.

On election night, he told cheering supporters he ran for "anyone that ever got knocked down that got back up."