Since voting for the non-Trump one is completely meaningless, voting third party actually has a greater real effect. It doesn't get the third party elected this time, but the larger the percentage of third party is per election cycle, the more it might seem possible to get one elected, and that might in turn lead to real perceptible changes. It might lead to, eventually, 16 years down the line, to a critical mass where enough people will think it's viable and get someone else elected. Or it might scare the existing power-monopoly into doing some democratic actions.
Since voting for the non-Trump one is completely meaningless, voting third party actually has a greater real effect. It doesn't get the third party elected this time, but the larger the percentage of third party is per election cycle, the more it might seem possible to get one elected, and that might in turn lead to real perceptible changes. It might lead to, eventually, 16 years down the line, to a critical mass where enough people will think it's viable and get someone else elected. Or it might scare the existing power-monopoly into doing some democratic actions.