Vice President Joe Biden's repeated laughter during Thursday's debate was a reflection of the "enormous amount of passion and joy" he brings to the job of serving the American people, White House press secretary Jay Carney said on Friday. Biden has drawn criticism for cracking up when Paul Ryan was talking about everything from Medicare to tax cuts to Iran's quest for a nuclear weapon. "The person I saw up there last night is somebody who is absolutely passionate about fighting for and defending the middle class... and who comes to his job -- this many years in to serving...