WASHINGTON — A US senator who suffered a stroke that upended the high-stakes campaign for one of the most hotly-contested states in last year’s midterm election is receiving hospital treatment for clinical depression, his staff said Thursday.

Pennsylvania’s John Fetterman — who made headlines for his imposing stature, unconventional dress style and easy, relatable charm — had only just returned to work after becoming lightheaded and going into hospital last week.

The 53-year-old Democrat’s doctors determined at the time that he had not suffered another stroke, his office said.

“While John has experienced depression off and on throughout his life, it only became severe in recent weeks,” his chief of staff Adam Jentleson said in a statement.

The senator agreed with advice from medics in Congress that he check himself into Walter Reed National Military Medical Center, a 45-minute drive north of the US Capitol.

“After examining John, the doctors at Walter Reed told us that John is getting the care he needs, and will soon be back to himself,” Jentleson added.

Fetterman’s victory in a key swing state was seen as one of the Democrats’ biggest prizes in November as they went on to win what had once looked liked an improbable 51-49 majority in the upper chamber of Congress.

It was one of the most heated and closely contested races of the midterms.

Fetterman, who stands at six foot eight inches (2.03 meters) and was notable for his ever-present hoodie and shorts on the campaign trail, defeated celebrity doctor Mehmet Oz, who had the endorsement of former president Donald Trump.

But his stroke five months before the vote severely curtailed his public appearances, as he revealed that he had “almost died.”

“After what he’s been through in the past year, there’s probably no one who wanted to talk about his own health less than John,” his wife Gisele Fetterman tweeted.

“I’m so proud of him for asking for help and getting the care he needs.”