Third Parties are supposed to represent democracy in action, but we have now learned the hard way that it denies popular vote winners the Presidency!
It happened in 2000, when Ralph Nader and Pat Buchanan took enough votes away to harm Al Gore, and elect George W. Bush.
And now it has happened again in 2016, with Gary Johnson and Jill Stein taking enough votes to harm Hillary Clinton and elect Donald Trump.
Bush did much harm in his Presidency, and realistically, Donald Trump can be seen as likely to do even greater damage.
Any one who voted third party in 2000 or 2016 should feel guilt, as it has led to the worse choice, and nothing was accomplished, except maybe to feel good that one protested.
There is no way to prevent third party movements, but it has NEVER had a positive effect, with maybe the exception of Theodore Roosevelt’s Progressive (Bull Moose) Party in 1912.
But in a democracy, nothing can be done to prevent this harmful action from taking place, so likely, we will lose the better Presidential nominee more times in the future!