Stein is a fringe candidate and Johnson continues to reinforce the narrative that third party candidates are ill equip to be president with his Aleppo and not being able to name a single world leader gaffes. And then of course for people in swing states and even states at the margin people don't want to, as they see it, waste their vote. I actually think the Libertarian ticket would be better served with William Weld at the top and someone else as a running mate. I think Johnson has demonstrated a lack of ability to handle a presidential campaign. This was the Libertarians chance to have a great showing. 5% is their goal. They might still hit that, but they need to stop dropping in the polls (it's usual for third parties to plummet in support as election day nears).