I refuse to vote for 4 more years of Jared and Ivanka
Then vote Trump's rightward challenger in the primary, vote Republican in the election, and donate to the Alt-Right.
Two-party system is binary. Maximizing influence requires making a binary choice.
Evil wins because good is dumb.
Think of it this way. What if, instead of 1 person, you were 1 billion people. Would your voting strategy achieve your desired result then, or not?
Your vote for should maximize the following sum:
odds of candidate winning * ideological match
Eliminate candidates with a 0 for either, then choose between the remaining.
If you won't vote unless you get a close-match candidate, then the establishment can disenfranchise you indefinitely by blocking a close match from participating. But if you vote by the above formula, then you will shift the establishment in your direction over time, even if it starts completely hostile to you.
There are other reasons to skip voting, but this is the pragmatic political calculus.