It's a long-distance feud, transmitted over the airwaves and on social media, that's now devolved well beyond a small political spat.
For President Donald Trump and his predecessor, Barack Obama, the animosity that started years ago has never waned, except for a month-long period during the presidential transition.
Now, the current and former president are carrying out the nastiest public dispute in modern presidential history, one that began on deeply personal terms and which now plays out nearly every time Trump finds a policy he dislikes or a perceived double standard.
