Rather than withhold your vote for President, may I suggest that you either a) vote a third party candidate who better matches your values, or b) do a write-in if your state permits it.
Either of those, while they won't win the election, will allow you to cast your vote in a way that expresses your unhappiness with the offerings of the two establishment parties, and shows better your support for your own values.
I plan to write in Sarah Palin, because I believe she is the best we have for America. It pains me that she's not running, but since I can't get behind the establishment twits, I will express my support for someone who I believe represents the best match with my own values.
Respectfully submitted for your consideration.
Actually, what I actually meant was I would be, for the first time in my life, not voting for one of the candidates for one of the two major parties. But I will put SOMETHING there. Sarah, Virgil, something...