As “Girls” star and Brooklyn’s own Lena Dunham stumps for Democratic presidential front-runner Hillary Clinton, her television co-star Alex Karpovsky, who lives in the borough’s Greenpoint area, is backing rival Bernie Sanders.

Mr. Karpovsky, who plays Ray Ploshansky on the Brooklyn-centered television show, said about half of his friends are supporting Mrs. Clinton. “We’ve kept the discussions pretty civil,” he said.

This...