They will leave the national ballot blank. I am having serious trouble with the illegal immigration issue, even though I highly approve of him in other areas. I see the cozying up to illegals as being a breach of his oath of office. I will probably hold my nose and vote for him, because he is better than a RAT.
I will probably hold my nose and vote for him... Well, that's alot smarter than cutting it off! ;-)
Seriously, if there are those who find themselves to be unmotivated by the President's reelection efforts, the best thing they can do is find positive and creative ways to expend their energy for the next year. There will be a ton of solidly conservative candidates for other offices that will need support.