We have a ballot with three candidates and three ranked choices. What I'm wondering is if there is any difference between voting someone as third choice and not selecting a third choice at all. Are there any situations under which a different result could occur, like perhaps in a tie breaker?
You can use as many or as few of your votes as you like.
However, if there are three positions available or many more candidates than positions it makes sense to use all three votes.
In this election there's only one position available and only three candidates so you could just use one vote for the candidate you want to get the job as it's quite likely (though not certain) that there'll be a definitive result after the first round of voting. If you think that the won't be a result from the first round then it makes sense to use your other votes to indicate where you'd like your vote to go if your candidate is eliminated.
If there were more positions available or more candidates then your 2nd and 3rd votes would come into play once the candidate with the most first votes has been elected or if your 1st choice was eliminated.
However, if you only like one (or two) candidates then only use one (or two) votes. Please don't vote for someone - even as a second or third choice - if you don't think they'll make a good moderator.