If I have a choice between two candidates, neither of whom I like, is the morally responsible thing to not vote, because I then wouldn't be causally implicated in either of them coming into office?

That's certainly one acceptable response. Others might include voting for a third candidate if one is available, writing in a candidate's name if the ballot allows, or, in extremis, spoiling the ballot as a protest.

There's another issue worth raising. One might ask whether one's dislike of a candidate stands up to scrutiny. In this Presidential election, many people claim that they dislike both major party candidates. But a couple of things to bear in mind.

1) Personal dislike, as in "I find him/her obnoxious" doesn't strike me as a very good reason to vote against someone, especially if there's a lot at stake. What one might more reasonably care about is whether the politician favors policies that one find acceptable, and whether s/he will be effective at promoting them—whether or not s/he is someone whom you find obnoxious. Is what you find obnoxious just a matter of personality? Or is it a symptom of something that matters for larger reasons?

2) Is the dislike based on good information? Here I'll be more specific. Both candidates this year have very high negatives. But in the case of one of the candidates—Mrs. Clinton—the reasons people give for disliking her often don't stand up to scrutiny. There's been a good deal written about this. Old accusations can take on a life of their own and get repeated long after they've been debunked. This year, in Mrs. Clinton's case, this appears to be particularly so. But she's hardly the first politician to find herself in this position.

Just to be clear: Mrs. Clinton is an example rather than the issue. I have no problem at all with the idea that someone could vote against Mrs. Clinton for principled, well-informed reasons. But as it happens, I'm someone who had a negative impression of her, and I found, once I started paying attention to the evidence, that my impression had been largely based on misinformation, albeit misinformation that had attained something like the status of "common knowledge." Thus I'm using her as an example to help make a point: it's worth asking if one's reasons for disliking a candidate are good reasons, based in evidence, and relevant to what would happen if s/he were elected.

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