One way of getting around the disadvantages of TRS is to merge the first and second round into one election. There are several ways of doing this. AV is one obvious solution; it is used to elect the president of the Republic of Ireland. A lower-placed candidate who picks up many second-preference votes can overtake higher-placed candidates. The most recent example of a president winning through the transfer of preferences in this manner was the 1990 election of Mary Robinson to the Irish presidency.
A second possibility is the preferential system used for presidential elections in Sri Lanka and for London mayoral elections, known as the Supplementary Vote. Voters are asked to mark not only their first-choice candidate but also their second (and, in Sri Lanka, their third) choices. The way in which this is done differs: in Sri Lanka, voters are asked to place the numbers ‘1’, ‘2’ and ‘3’ next to the names of the candidates, in the same manner as unde r AVand STV. In London, no numbers are required; the ballot paper contains two columns, for a first-choice vote and a second-choice vote, respectively. Voters are asked to mark their first-choice and second-choice candidates accordingly. This means that voters do not have to write in any numbers themselves.
Counting is the same in both cases: if a candidate gains an absolute majority of first-preference votes, he or she is immediately declared elected. However, if no candidate gains an absolute majority, all candidates other than the top two are eliminated and their second- (or, in Sri Lanka, second- and third-) choice votes are passed on to one or the other of the two leading candidates, according to the preference ordering marked. Whoever achieves the highest number of votes at the end of this process is declared elected.
The disadvantages of the Supplementary Vote system include its additional complexity and the fact that voters are effectively required to guess who the top two candidates will be in order to make full use of their vote. Despite these differences, both AV and the Supplementary Vote have the same core aim: to make sure that whoever wins the election will have the support of an absolute majority of the electorate. The use of preference votes to express a second choice means that a second round of voting is not required, and this results in significant cost savings as well as benefits in administrative, logistics, and security terms.
