I clicked "Change My Vote" in a poll, made the change, but did not see the difference (I probably already voted that way). Not important anyway.
However, to check, I clicked "Change My Vote" again, and the number of choices to vote for doubled.
Then I tested, and every time you click, you get an additional set of choices.

Voting for any of the extra options still count your vote correctly.

Another bug is that if you check "Skip this poll and view results", your vote is taken away but the radio selection you voted for is still selected when the page returns.