Kamala Harris on Thursday defended Joe Biden's fitness to serve as president and blasted her fellow Democrats for "piling on" after his disastrous debate performance exposed the cognitive decline she helped conceal. "I feel very strongly that, um, I mean, it's an instinct of mine to be, um, someone who does not participate in piling on," she told Stephen Colbert during an appearance on the Late Show to plug her new book about the election. "And I was not going to pile on. And I just wasn't