Electoral systems revision: Supplementary Vote in operation

There is a strong possibility that in today’s London Mayor race second preference votes may well determine who gets to control City Hall for the next 4 years

Supplementary Vote in operation

For the elections I am not going to speculate on the implications of the outcome of the local polls in terms of what would happen if Labour drop to 25% or lay out the case for and against the two main candidates for London Mayor since these two issues are well covered in today’s national newspapers.

Instead I want to use the space to clearing up a few misunderstandings about the operation and workings of the Supplementary Vote system, and point out that in today’s London Mayor race second preference votes may well determine who gets to control City Hall for the next 4 years.

The Supplementary Vote is used in London mayor elections. If a candidate wins more than half of the first choice votes, then they are elected. If no candidate wins over half of the first choice votes, then all but the top two candidates are eliminated and losers’ second preferences redistributed.

This is often confused by candidates with the Alternative Vote where voters also vote for their 1st and 2nd preferences but votes are redistributed from the bottom candidate and this process is repeated until a candidate gets over 50%, i.e. not all of the loser preferences are redistributed at the same time.

SV is therefore a majoritarian system since the winner needs over 50% of either the 1st preference votes or the 1st and 2nd preference votes together – since the 2nd preference voters effectively become 1st preference votes once the other candidates are eliminated the winner can claim a mandate from the majority of voters.

In the 2000 contest, Livingstone was clearly ahead on both the 1st preference and the combined 1st and 2nd preference count – although Norris did pick up slightly more 2nd preference votes therefore hinting at the capacity of the system to defeat the 1st preference winner

In 2004 the story more or less repeated itself, but this time Livingstone picked up the largest number of both 1st and 2nd preference votes.

This year it is predicted that the race between Boris and Ken is so tight that the candidate that wins most 1st preferences could lose if they pick up less 2nd preferences, and obviously vice versa. With Brian Paddick refusing to declare who he would like his supporters to give their second preference to, voting analysts have been unable to give clear predictions as to the outcome. We will know more at some stage in the next 48 hours.