Rather than re-hash all the familiar reasons to vote for MMP in the upcoming referendum, here’s a new one I haven’t seen discussed.
MMP is not a perfect electoral system – because there ain’t no such thing. But it’s pretty good, and because we’ve been using it for fifteen years we know what most of the flaws are – and if we vote to keep it we get a commission to figure out how to fix those flaws.
But if we vote to get rid of MMP and replace it with STV, or Supplementary Member or whatever, those new systems might solve some of the problems with MMP but they’ll introduce new as-yet-unforseen problems that politicians will readily identify and exploit. So in another fifteen years we’ll still be complaining about the unfair electoral system and demanding that something be done about it.
If we keep MMP and fix the current problems we avoid another fifteen years (plus) of electoral system teething problems with whatever we replace it with.