While growing up I often heard the Jack Benny Show on radio, but I didn't know until yesterday that for 10-years Jack Benny did both a radio and TV show in the 1950s. This knowledge came from the Harry Shearer 'LeShow' yesterday on KDX. Harry attributes Benny as a mentor.
Jack Benny was one of the few radio stars that preferred that medium over TV. He managed to successfully adapt his spoken word style of comedy to a more physical one, but both worked. He was pretty much forced to give up his radio show in the early 1960s when most stations moved to a Top 40 format.
It's interesting that more physical comedy stars such as Milton Berle were more successful on radio than TV. Berle never did get the formula for TV. Red Skelton was the opposite. His radio shows were somewhat popular, but he never really broke out until TV.