Among Democrats, another convention hums in Sanders fans' phones

PHILADELPHIA (Reuters) - There is the Democratic convention unfolding onstage in Philadelphia this week, broadcast to millions on television. Then there is a second convention that exists largely hidden from public view in the smartphones of Bernie Sanders' delegates.

Using various messaging apps and secret Facebook groups, many of the delegates pledged to the U.S. senator and runner-up in the party's presidential nomination contest have been coordinating among themselves in Philadelphia.