The only halfway-plausible democracy-related argument against AV that I've heard is that coalition governments (which are certainly more likely under AV) are given to horse-trading, and end up delivering policies that no one voted for. And of course we have the current lot to prove that point, albeit they were elected under FPTP. However, this ignores how far politics is always about horse-trading - which, under the name "checks and balances" is sometimes thought to be a good thing - and how liable even single-party governments are to forget their policies when in power (as anyone who saw Labour break their promises on student fees not once but twice will recall). In any case, the remedy remains the same: parties that do this can be thrown out at the next election, if the electorate want to do it.
There's another kind of horse-trading, though, that AV does away with - namely tactical voting. While coalition negotiations about detailed policies take place behind closed doors, tactical voting under FPTP goes on in the even more confined forum of an individual voter's skull. It is also far cruder . You have to vote warts and all for one candidate/party or another, and will be assumed thereafter to have fully endorsed all their policies, even if you only did it in a sly, political way, to keep the other person out. Actually, it's not so much like horse-trading as getting taken to the cleaners at William Hill.
Other arguments against AV tend not to be about its democratic credentials. They are either very short term ("I'm not going to do anything that will please Nick Clegg!") or partisan ("AV will offer an advantage to [insert name of party you don't like here]")* or, slightly more respectably, stress the importance of having effective government ("Coalitions may reflect the wishes of the people, but they are weak, weak, I tell you! What we need is a strong Leader who will guide us out of this mess towards a New Dawn!"). Okay, I exaggerated that last one, but I do think that people who prefer Strong government to Democratic government should at least be clear that that's what they're advocating, even though it's not an all-or-nothing choice. In any case, their premises are far from certain, given that there are both strong coalition governments and weak single-party ones.
But I was spurred to write this post by something else Cameron said yesterday, later echoed by a "No" election broadcast. Both took the phrase "first past the post" and used it to make a horse-racing analogy. "If it's good enough for horses it's good enough for the voters," declared Cameron, before adding that candidates losing their deposits should be humanely destroyed. (Something like that, anyway - I can't find the link - but he certainly drew the analogy between FPTP and winning a horse race.) Which leads me to something I've occasionally wondered before: what is the "post" in "first past the post"? Clearly it's not any kind of percentage or numerical threshold of votes cast (that's the whole problem, from the point of view of those who don't like it) so how does the racing metaphor actually work? As far as I can see, AV is much more like the winning of a race. The "finishing post" is the 50% mark, and they keep counting votes until someone passes it. So, although it may seem a little late at this point in the referendum campaign, I suggest that the phrase "first past the post" should from now on be used exclusively of the alternative vote system, while the voting system previously known as FPTP should change its name to "More Votes than Any Other Individual Candidate", or MVTAOIC. Does that make sense?
* I loved Jason O'Mahony's observation on Iain Martin's recent Mail article: "the argument that FPTP should be retained because it is the only way the Conservatives can thwart the will of the British people is, to me, weak." Thanks to nwhyte for the link.