Currently there is a moderator election going on in Arqade and it's in the main portion of it where you choose specific candidates for positions ordered First, Second, Third.
I voted in it moments ago, but I accidentally put the wrong candidate in position First, and it was not immediately apparent how to switch a different candidate to that position (there was no close "x" in the corner, or a cancel button). After a brief experimentation, I did figure out how to correct my vote: the actual task of switching a candidate is done by simply selecting anyone else for the position.
This isn't obvious.
I think there should be a single sentence explaining how to switch your vote (similar to "To switch your vote in the main election, simply select a different candidate for that position.") somewhere on the page, possibly towards the bottom of the election sidebar.