Obama steps in as Clinton recovers By Kevin Liptak, CNN White House ProducerUpdated 10:56 AM ET, Tue September 13, 2016 Philadelphia (CNN)A cavalry of top White House Democrats -- President Barack Obama, First Lady Michelle Obama, and Vice President Joe Biden -- are arguing Hillary Clinton's case this week as the Democratic nominee herself is convalescing from pneumonia and absent from the trail. Nightcap: Hillary Clinton talks to CNN's Anderson Cooper about her health | Sign up In Philadelphia Tuesday, the President makes his first solo campaign appearance of the year, hoping to convince his diverse array of backers that...