Sorry, it’s my opinion and I think you, by voting third party at this time are turning your back on the Republic. You won’t change my mind. A third party vote helps Trump.
There are a lot of moving parts here. There are different reasons for throwing a vote away for sure. Some are so deluded, they believe:
A. Their candidate has a chance to win
B. Their candidate is qualified for office.
Others simply make a statement by throwing away their vote. In Doc's case, he hurts trump by making a statement. In a Red state, his vote would otherwise go to the Republican no matter how bad the candidate is. trump is just a bridge too far.
I'm sure we can agree that all elections are decided by a small handful of states. In those states, every vote counts and your premise rings true. In most states, the outcome is always 100% predictable.
However, IMO voting third party lumps you in with millions of fools who know absolutely nothing about the issues. At least, that's what the candidates see when they analyze data.
In '16, I simply didn't vote for POTUS. I made the decision long before the primaries were over. It was more of a boycott of the system, as I was disgusted by the way Congress moved to undermine Obama every single day. I came to realize that POTUS is often a figurehead with limited ability to achieve anything.
Living in NY, I had that luxury as Clinton won handily. I did vote down ballot.
When politicians analyze the data, they see me as apathetic instead of delusional, and believe that there must be a way to get me to vote. Perhaps they figure they need to offer better candidates. Third party voters will never recover from their delusions, in the eyes of the data crunchers.
Of course, trump proved that it DOES matter who POTUS is, but my refusal to vote did nothing to alter that outcome.
As an aside, I have a long time message board friend who always voted third party when he lived in California. He too had that luxury.
He moved to Pa a handful of years ago, and fully recognizes the need to vote Democrat. And he does.