I don't expect a large number of voters abandoning their major party this election, whether we're talking about Republicans or Democrats. Third party bids are always overhyped. And the fact that both nominees are rather divisive figures (and not wildly popular) may make the election even more polarized, rather than giving a third party a credible performance.
But much of the polarization is basically "negative partisanship". People support the candidate of one party because they hate the candidate of the opposing party so much. If the media actually gave some coverage to one or more third party candidates and treated them as a reasonable option rather than the candidate of cranks, some of those people might then move over to that third party candidate, especially in a year like this.
The only problem, for the media to do that would probably require a few of the more prominent #NeverTrumpers to talk up Johnson (or whoever else) as an option, and I'm not sure they would do that. Bill Kristol may not be ready to vote for Clinton or Trump, but I don't see him voting for Johnson either.
