Why the Alternative Vote electoral system is preferable to First-past-the-post

For those who haven't yet seen it, this is an excellent review of the Alternate Vote electoral system, by Dr Roger Mortimore http://bit.ly/hVgef2

As someone who favours a proportional system, I do see definite advantages to having a system like AV, over and above that of First-past-the-post. And to best explain the difference, we can think in terms of negative voting. By negative voting I mean to describe the situation whereby voters vote predominantly for the party which they consider to have the best chance of keeping out another, more feared, alternative. It is otherwise known as tactical voting, perhaps because of the 'negative' connotations of the word negative, but I do not mean to use it pejoratively.

If we assume the problem with First-past-the-post is that people have no choice but to vote negatively, and further that once they have made that choice they are limited to only one alternative, AV does offer a significant advantage. For someone who wants to keep a particular party out, under AV, they must simply (do no more than) vote for another likely winner in the second berth of their preferences. Unlike with Fptp, there is no urgency to make the tactical choice the first preference because, provided the feared candidate is rejected on the first preference, as would be natural, the race is not over (unless the feared candidate has already won, and tactical voting has become irrelevant) until at least the next stage of preferences will be taken into account. This means that, in effect, with AV voters get an extra choice (for tactical voting and rejection) above Fptp, which means they are able to vote tactically with their first preference (rejecting their second preference choice) and also with their second (rejecting the most feared mainstream party, this would be their traditional Fptp vote now relegated to their second choice).

With Fptp, voters are able to reject only one of the mainstream parties, with AV voters are able to reject certainly two (the second rejected candidate being that of their chosen second preference) which is preferable since this gives a better expression of the voters' wishes at the ballot box, and in the final analysis.

A party which appears as second preference has still been rejected, only to a lesser degree than a party which is absent entirely from the list of all preferences.

The Alternative Vote gives voters an extra tactical choice, compared against Fptp.