That Mr. Biden could not do better outside the cities and close-in suburbs has made many Democrats pessimistic about what’s possible in those areas. Mr. Fetterman’s background, his attention to the state’s rural communities and his manner — the work clothes, a straightforward speaking style — could make some difference. In the winning Fetterman model, he narrows the massive margins that have been run up by Republicans.

His positions do not differ that much from more traditional Democrats’, but some of his central concerns do set him apart. A signature issue has been the legalization of marijuana — “legal weed,” as he calls it. He has flown a flag displaying cannabis leaves from the official lieutenant governor’s office, alongside a rainbow-colored L.G.B.T.Q. banner.

The advocacy of legal marijuana may be the rare issue that draws support from unpredictable corners and crosses all kinds of lines — including urban and rural.