Hillary Clinton finally apologizes for private email server: 'That was a mistake. I'm sorry about that.'

After months of defending her use of a private email server during her time as secretary of state, it seems Democratic presidential frontrunner Hillary Clinton has had a change of heart. In an interview that will air Tuesday evening, Clinton sits down with ABC's David Muir, marking her second national interview in a matter of days, but only her fourth since her campaign launch. Ahead of the broadcast, Muir tweeted: NEW @HillaryClinton on her private e-mail server: "That was a mistake. I'm sorry ...