Understanding the Supplementary Vote

The Supplementary Vote (SV) is a shortened variation of the Alternative Vote (AV) system, tailored for the election of single office-holders within regional or local authority areas. This system, which has been in use since the early 2000s, offers a simplified approach to electing officials while still ensuring that a significant portion of the electorate’s preferences are accounted for.

How Supplementary Voting Works

In the SV system, voters are presented with the opportunity to express both a first and second preference on the ballot. The process begins with the counting of first-choice votes. If any candidate secures more than 50% of the first preferences, they are declared the winner outright.

However, if no candidate achieves this majority in the initial count, the two candidates with the highest number of first-choice votes proceed to a second round. During this round, the second-choice preferences of voters who initially supported candidates that have been eliminated are factored in. These second-preference votes are added to the remaining candidates’ tallies from the first round. The candidate with the highest overall count after this redistribution process is declared the winner.

The Pros and Cons of Supplementary Voting 

The benefits of Supplementary Vote

  • SV encourages strategic campaigning, as not only first choice but also second choice votes are important.
  • SV gives the voter more power because both first and second preferences may count.
  • SV is a simpler system to understand compared to AV.

The disadvantages of Supplementary Vote

  • SV can promote voting for candidates from the main parties only.
  • The winning candidate need not have the support of at least 50 per cent of the electorate under SV
  • If voters think there will be no clear winner after round 1, they must guess which two will make the final round and allocate their choices accordingly. It is possible for voters to inadvertently defeat their preferred candidate.
  • By the nature of SV there can be a lot of wasted votes; because the votes cast in the first round may end up not being transferring and notcounted in the second round
  • Under the SV system there is a likelihood of tactical voting.


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