“I’m a big fan, he’s a great guy. So lay off him, he’s doing great,” the British songsmith said on Tuesday, ABC News reported. This year’s recipient of the Library of Congress’s Gershwin Prize for Popular song, McCartney is set to perform at the White House Wednesday evening and be feted by fellow musicians Stevie Wonder, Faith Hill, the Jonas Brothers, Elvis Costello and Herbie Hancock, among others. Speaking at a press conference in Washington ahead of the event, McCartney, 67, said he planned to “try to have fun” but predicted a case of the nerves when performing “like, three...