imo Johnson could do well but probably wouldn't break 3%. But that 3% could decide close states either way (and if turnout is similar to 2012, that's 4 million votes right there)
The West is generally fertile territory for Libertarians. Johnson got 3.6% of the vote in New Mexico in 2012 (his home state), and could definitely add a new dimension to Nevada and Colorado if he's getting 3% of the national vote.
If 2016 comes down to the wire, a strong Libertarian performance could act as a serious spoiler for either Hillary or Trump. Romney beat Obama in North Carolina by 92,000 votes, while Johnson took 45,000 votes (i.e. about half the margin needed to flip the state).
Of course, I doubt the Libertarians will significantly improve on their 1%; in fact they might actually fall. But if it's a close election, there is always the possibility they could unintentionally act as a spoiler in one or more states.
