Like other former British colonies, Sri Lanka inherited a Westminster model of parliamentary government, with universal suffrage established in 1931 and full general elections in 1947, but over time found that First Past the Post (FPTP) elections were incapable of representing minority interests, see First Past the Post (FPTP). In 1978, the decision was taken to transform Sri Lankan government from a parliamentary system into a French-style executive presidency, and a Select Committee was appointed to consider the necessary wide-ranging constitutional changes.
Sri Lanka is a nation with a long history of bitter ethnic conflict between the majority Sinhalese and minority Tamil communities. It was for this reason that the constitutional drafters were very conscious of the need to ensure that the new office of executive president would be filled by a national figure representative of all groups in society, and capable of encouraging consensual politics between those groups. The new president would have to represent all groups in Sri Lankan society and be seen as a figure capable of moderating between opposing interests. These objectives focussed attention on the method of election to the new office, and particularly on the means by which ethnic minorities could be included in the selection process.
While the method of election for such a figure would be crucial to the fate of the office, and would require at least a majority of voters supporting the successful candidate, only once in 50 years had any political party secured a majority of the vote at a national election; indeed, most governments had been elected with considerably less than that. The party system in Sri Lanka was fragmented between two dominant Sinhalese parties and a number of small minority parties.
Because much of the 1978 constitution had its philosophic origins in the French Fifth Republic model of a strong executive presidency combined with an elected legislature, the initial plans provided for a Two-Round System (TRS) of presidential elections, see Two-Round System. However, the extra cost and security issues associated with holding two separate elections within a two-week period was seen as being a major defect, particularly since Sri Lanka was in the midst of a violent civil war at the time.
These considerations prompted an innovative solution to the problem: to combine the initial and run-off rounds of voting into one election via the expression of preferences. Under this system, which continues to be used, if no candidate has a majority of first preferences, all candidates other than the two leaders are eliminated, and the second preferences distributed to one or the other of the top two to ensure a majority winner; voters can number up to three preferences, which will then be distributed to one or the other of the top two candidates in the event of no candidate having an absolute majority. The system thus achieves in one election what a Two-Round System achieves in two, see Alternative Vote.
In addition to ensuring that the president would be elected, whether outright or via preferences, by an absolute majority of all voters, the system has the additional feature of encouraging candidates to look beyond their own party or ethnic group for second-preference support from other groups. Sri Lanka has now conducted three national presidential elections under the supplementary vote system, in 1982, 1988, and 1994. Contrary to expectations, at each of these elections the winning candidate has achieved an absolute majority in the first round, and thus no preferences have been counted. The possibility that preferences may one day decide the result, however, does appear to have influenced the campaign strategies of Sri Lankan parties, and there is considerably more attention paid to minority groups in election campaigning for presidential elections than was formerly the case.