While I more or less used to give these people a pass (since, hey, if that's the most important thing to them, then maybe nothing else does matter in their minds), even if I disagreed with their position, I now find myself getting all riled up on the issue. Like, to the extent that I sometimes think it is fundamentally immoral to vote on one thing alone.
Certain family members of mine will say things like, "Well, I don't agree with all that stuff that the social conservatives want, but taxes matter most to me." My response is that these family members are still making those other things (like constriction of civil rights) happen, and they have a moral obligation to admit to that. And this doesn't only go one way; it's just that the Republican single-issue voters have been more visible and more exploited in recent years.
But maybe my blood pressure is rising because of the stress of the election season, and I'm not thinking rationally. What do you think about single-issue voting? Is there one issue for you that trumps all others and would change your vote?