The Monmouth poll not long ago showed at Gary Johnson (possible Libertarian nominee) pulls votes slightly more from Hillary than Trump.   Mostly, it's about even-steven, but when people realize that our candidate was a two-term governor, elected as a Republican, the odds are that the LP  will make a sizeable dent in duopoly percentages.   If Bernie is not the Dem nominee, many Bernie supporters will come over to Libertarian, too.