In yet another great diavlog, Will Wilkinson talks with Jason Brennan about his thesis that some people should refrain from exercising their right to vote. The argument seems clear enough: people who vote badly make the world worse, and you shouldn't do that without damn good reason. (See also the discussion at Crooked Timber.)
Now, you might claim that people are obligated to vote well. But as a matter of non-ideal theory, it doesn't follow that they should vote (simpliciter). Whether they should vote depends on whether they actually would vote well or badly. Clearly the ordering of the possible actions, from best to worst, is:
(1) Vote well
(2) Don't vote
(3) Vote badly
Merely saying 'vote', simpliciter, does not provide sufficient information to determine whether it's advisable or not. That's true even if you think option 1 is obligatory, because committing an egregious wrong  rather than a minor wrong  is all the worse -- not something to be advised.
In any case, I don't think there's any good reason to think that voting is obligatory. Most positive demands aren't. [See also my post 'Against Moral Mindfulness'.] Perhaps we have an 'imperfect duty' to serve the common good in some or other fashion, but there are obviously any number of ways to do that, and there's no particular reason to privilege voting above all the rest. (Jason makes this point nicely towards the end of the diavlog.) It takes a fair bit of time and effort to become a responsibly informed citizen, and it's not hard to imagine better things one might do with those resources.
Curiously (you might think), I actually think there's a strong case to be made for compulsory voting -- or rather compulsory attendance at a voting booth on election day. But that institutional recommendation is compatible with the above moral directives. Anyone likely to vote badly can fulfill their legal and moral obligations alike by turning in a blank ballot.
Finally, I want to raise some doubts about one of Will's claims. He infers from Jason's thesis that "many voter participation initiatives promote pretty straightforwardly immoral behavior." A couple of thoughts:
(i) They're not encouraging people to vote badly, but simply to vote. My above discussion suggests that this is neither determinately good nor bad, but rather morally ambiguous behaviour. Some people they encourage will go on to do good, others will do something bad. Hopefully the former group is larger. This brings me to my second point:
(ii) Encouraging a particular form of "immorality" in others is not necessarily itself a bad thing, if you can foresee that this will have good effects. As Will points out, the effect of voter turnout drives is to increase the Democrats' electoral chances. One might plausibly consider this to be a good thing. There are significant numbers of people who act immorally in voting for Republicans. (That's not to say every Republican supporter is unjustified or immoral.) It's not obvious to me that there's anything wrong with attempting to counterbalance their wrongdoing, even by means of encouraging comparably ignorant Democrats, so long as the people pulling the strings are really (and reliably) acting for the best. Two 'wrongs' might make a 'right' after all.
Update: Jason has more up at Public Reason.