Re: A Vote is an endorsement
The problem is the people who consider themselves democrats or republican - not just those who are registered but those who like to claim themselves as independents but maybe only one time voted for a different party for president.
There are undoubtedly plenty of democrats and those who lean democrat who are not excited about the prospect of voting for Hillary, and there are an equal number of republicans and those who lean republican who are not excited about the prospect of voting from Trump.
Unfortunately all they hear from their friends (especially those who live in echo chambers and mostly surround themselves with other democrats or other republicans) is "OMG you have to support [Hillary|Trump] even if you don't like [her|him] or we'll end up with [Trump|Hillary] as President and America is done!" plus a lot of "this is the most important election of our lifetime" (i.e. the same thing that is said about almost every presidential election)
The true independents and those who support different parties (green, libertarian, etc.) are not large enough in number to make an impact by supporting third parties. The democrats and republicans who are not happy with their choices have to get over their irrational fear of the "wrong" candidate winning and stand up to their friends who will tell them that if they vote third party it is the same as voting for the other guy. Or heck, if they just won't shut up about it, let them believe you will vote the way they think you should, but do your own thing in the privacy of the voting booth.
Libertarian candidate Gary Johnson is on the ballot in all 50 states. He's been a republican governor, and his running mate has been a (rather liberal) republican governor as well, so they aren't some crazy nutbags who subscribe to the ridiculous libertarian fantasies about privatizing roads and all that crap. They're serious guys with actual governing experience who can do the job, and they're worth a look. Certainly for disaffected republicans who don't subscribe to the social conservatism that has taken over the republican party in the past few decades, but also for disaffected democrats who think that they've lost their way in supporting too much government with things like free college tuition. With a little more support he can make the presidential debates this fall, and presented with a reasonable third choice there could be a lot of defections from both parties into his corner from people who don't want to see either Trump or Hillary in the White House. He's a longshot, but given the two main choices this is the best chance a third party candidate has had since '92 and one that might not come again for another 20+ years.
Green party candidate Jill Stein is on the ballot in only 29 states, and doesn't have the actual governing experience of the libertarian candidates, but she's certainly an alternative for disaffected Bernie supporters who would have a really hard time casting a vote for Hillary and definitely wouldn't consider Trump. She won't make the debates, but voting your conscience isn't a wasted vote even if she doesn't have a chance of winning.