Why David Cameron's NO to AV race analogy is wrong.

On at least three occasions I've seen David Cameron use a race analogy in his desperate attempt to discredit the Alternative Vote. On Friday 1st of April in Wales he said this:

"and it's a system that's so unfair that a candidate which came second or third can end up winning. Just think forward to the Olympics; Usain Bolt powers home in the hundred metres when it comes to handing out the Gold Medal they give it to the person who comes third. You wouldn't do it in the Olympics, we shouldn't do it in politics we've got to vote no this crazy system." 

Well David Cameron is wrong to compare electing an Member of Parliament with a race because firstly with First-Past-The-Post there is no post or finish line. An MP can be elected with as little as 29% of the vote so if I were to use David Cameron's race analogy I would say:

"Just think forward to the Olympics; Usain Bolt powers along to 29 metres and then everyone just stops running and they give him the Gold Medal even though no one finished the race or crossed the line... in fact there IS no finish line. You wouldn't do it in the Olympics, we shouldn't do it in politics we've got to vote no this crazy system... vote YES to AV on May 5th"

Secondly neither system can be compared with a race because electing an MP is about constituents choosing a person to best represent them in Parliament and not a popularity contest, (or a race) - because AV enables at least half the voters to choose their MP it is more democratic than First-Past-The-Post - which more often than not results in less than half the voters electing their MP. But if David Cameron insists on using his NO to AV race analogy I would answer him by saying; at least the Alternative Vote has a finish line to cross, (50% of the vote) which is more than than can be said of First-Past-The-Post!