This is not to find out who you're voting for, that's your business. I simply want to know your motivation. Are you voting for a candidate because you like his / her position on issues or mostly voting against that candidate's opponent?
I think using your vote "against" someone is a terrible way to spend your input.
In this election, there is almost no reason to vote for either one of the major candidates.
So while it may be terrible it is reality.
As far as I'm concerned, if you're going to vote, then take it upon yourself to find a candidate that you can vote for in good conscience. I've never voted Democrat or Republican in a presidential election, and this year will be no different. There are others out there, and while they won't win, it is important that my vote be in line with my beliefs and values. If nobody is present that I wish to vote for, I write in. If I can't write in, then that is when "against" comes into play, and I express my "against" vote by abstaining.
I have voted 3rd party before but the third party candidates this year are awful. I voted for Gary Johnson in 2012, as vote swap, but he is demonstrably worse (less informed, lower energy) this year than in 2016.
Jill Stein is almost Trump level dangerous, from her absurd anti-vaccine positions, to her ruinous economic plans, and her even more naive foreign policy views than Trump, or Johnson.
To be honest, if you couldn't find either McCain or Obama worthy of your vote in 2008, then I doubt you'll ever vote for winning Presidential candidate in your life. They were about as good candidates as America every gets or frankly deserves.
I'm voting for Hillary, because she is the only candidate that I find that meets the bare minimums to be President,but primarily I'm voting for her to keep the worse candidate ever Donald Trump out of office.