Unfortunately, that means that you're taking a vote away from the candidate from the two main parties that is closest to your views, which helps the candidate you oppose the most.
The two party system is truly problematic, but when it comes to November you have two options currently and voting for a 3rd party has the same impact as not voting at all. Voting for the candidate that you oppose the least lets you put a finger on the scale to at least try to avoid the worst possible outcome relative to your beliefs and values.
*Second best army in Russia