Possibly, the gap will close between the two major candidates and the race between them might be close enough that a third-party vote would “spoil.”
Voting third-party may be meaningful in the 2016 US election
Matthew Ivan Bennett

But spoil the race for whom? Both candidates are so abhorrent that it’s impossible to decide which one is worse. There’s no “lesser evil” this election. (I’d venture to say Gary Johnson because, while I don’t agree with Libertarianism, I find him preferable than Trumpary.)