I think 321 lets you have as many good/bad/ok candidates as you like. The thing it doesn't allow is marking a candidate as, say, both good and bad at the same

I think 321 lets you have as many good/bad/ok candidates as you like. The thing it doesn't allow is marking a candidate as, say, both good and bad at the same time. (I'm not an expert though, I just heard about 321 yesterday, and my source of knowledge is the most plausible-looking google search result.) I agree that a likelihood of higher-than-normal percentage of spoiled ballots is a potential problem with IRV, at least with mail-in or in-person paper ballots. Voting machines shouldn't have a problem with it. Approval is about as simple as it gets. In order to spoil the ballot you'd have to do something pretty strange like tear the ballot in half. Or with mail-in ballots, the usual things like not signing the envelope (assuming that's required in your state) or mailing it too late to arrive on time. I don't see ballot spoiling as necessarily a show-stopper for using RCV on its own, but there are other compelling reasons not to use it (such as failing monotonicity).