What is foolish is to "vote for a person." You are voting for someone likely to implement one or another set of policies within the context of a rather established political system. You're voting that certain legislation be vetoed, certain political appointments are made, and certain political initiatives be promulgated. To a rather unfortunate extent, you are voting for a foreign policy with worryingly few checks on them.
Those are what you vote for. Not for the most likeable guy or even the person you agree with the most: you are trying to influence near-term policy decisions. No less and no more.
I am in a safe state for the one of the two candidates from the major parties that I would prefer be elected, so I can spend my vote to send a political message in the longer term, however. In that case, I am voting for a policy direction that is currently off the mainstream political radar, but which I'd like to see enter into the realm of actual politics at some point. If there were any doubts about my state's outcome, however, I would hold my nose and choose the major party candidate.