evidence: 3. Take the party with the smallest number of first-preference votes and change each vote for that party by removing the first-preference votes and turning th-preference votes into th-preference votes for each 4. Remove that party from the list of preferences of all other voters. [...] Why might you want to change your first preference if the party you voted for is still in the running? I can think of a few reasons. One is that you might want to vote tactically because of something like the scenario I outlined earlier that can occur under AV: you want to eliminate a party so that the party you actually like can pick up votes from the supporters of that party. Another is that you like backing a winner, and you sense that a candidate has "momentum". The first reason is a legitimate one but an undesirable feature of MR (so it is good that AV lacks it). The second is not, I think, rational in a vote for an MP, though it might be rational if you are voting for a party leader and want a display of unity. [...] Here is a different argument. Suppose there is a constituency with four candidates, representing Labour, the Conservatives, the Liberal Democrats, and the British National Party. The first preferences are