One of the keys of Mr. Biden’s comedic appeal is his willingness to play along. “A smart politician just goes with it,” said Ted Widmer, a historian at Brown University and a former speechwriter for President Bill Clinton. Mr. Widmer said the vice president’s embrace of the Onion’s fixation on him shows a level of acceptance that other politicians can learn from. “These things can’t be stopped anyway,” Mr. Widmer said. “It’s a virus, out of control. So you might as well participate and have fun. It shows a quality of humanity.” This was on shiny display last week — like a showroom Corvette — as The Onion released its e-book autobiography of Mr. Biden. The Onion Biden — a k a “Diamond” Joe Biden — participated in a Reddit “Ask Me Anything” thread to promote “The President of Vice.” To top that, the vice president himself — the real precious cargo! — tweeted in, declaring “#imavetteguy” to his Onion alter-ego. This was later re-tweeted by the president’s account.