To connect with a radio audience, you have to possess a voice that people like listening to, a personality they want to welcome into their homes every day, and the ability to discuss and defend your beliefs respectfully for hours at a time. Franken talks very slowly, his humor comes from an arrogant viewpoint, his delivery fairly drips with condescension, and he can't make an argument without attacking someone personally. Note that he couldn't even get through the title of his book about Rush Limbaugh without calling him a "big, fat idiot." And it's no accident that his most famous SNL bit was the "Al Franken Decade," which had the repetitive punchline, "Me...Al Franken."
IMHO, he's going to crash and burn very quickly. If he stays on the air more than six months, it will be because some rich liberals have too much money to flush away and no toilet handy.
Didn't Frankin do a skit on SNL where he said "I am a Communist"?
I found it believable.