WASHINGTON — Senator Fetterman, the Pennsylvania Democrat who suffered a stroke during his campaign last year, was hospitalized Wednesday night after feeling lightheaded while attending a Senate Democratic retreat, his office said.

Initial tests at George Washington University Hospital did not show evidence of a new stroke, Mr. Fetterman’s communications director, Joe Calvello, said in a statement issued Wednesday night. 

Doctors were running more tests and the senator remained at the hospital for observation, according to the statement.

“He is in good spirits and talking with his staff and family. We will provide more information when we have it,” Mr. Calvello said.

Mr. Fetterman, 53, succeeded Senator Toomey after a hard-fought contest against Republican nominee Dr. Mehmet Oz. He defeated the celebrity heart surgeon by 5 percentage points and flipped a seat that was key to Democrats holding the Senate majority. 

More than $300 million was spent during the campaign, the most expensive for the Senate in 2022.

His campaign was derailed on May 13 when he suffered what he later called a near-fatal stroke. He refused to drop out and spent much of the remaining months of the campaign in recovery, refusing to release his medical records or allow his doctors to answer reporters’ questions.

Dr. Oz made an issue of whether his opponent was honest about the effects of the stroke and whether Mr. Fetterman was fit to serve, but the Democrat insisted his doctors said he could have a full recovery.

In an Associated Press profile just weeks after his victory, Mr. Fetterman was described as still suffering from auditory processing disorder, a stroke’s common aftereffect. 

The disorder can leave a person unable to speak fluidly and quickly process spoken conversation into meaning.

The effects of the stroke were apparent in Mr. Fetterman’s uneven performance during the fall campaign’s only debate. 

He struggled to complete sentences and jumbled words, causing concern among Democrats that his election was doomed.

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

Mr. Fetterman, a presence at 6-foot-8 with a clean-shave head and a goatee and known for wearing hoodies and shorts, was the state’s lieutenant governor from 2019-2023. 

He served as mayor of Braddock, Pennsylvania, from 2006-2019.