When he was running for US Senate in 2008, Democratic candidate and former “SNL” writer and star Al Franken and his minder Kris Dahl played a prank on a political rival. The pair devised a plan to foil a Republican staffer who’d been dispatched to film Franken at public engagements, by inventing a tedious, never-ending debate about the purchase of a pullout bed. “Every time we got out of the car, we’d pretend we were in midconversation,” Franken writes in his new book, “Al Franken: Giant of the Senate.” “Kris would emerge from the driver’s side first. Stepping out of...