The current U.S. election method, in which voters name one--and only one--candidate, is called plurality voting. In elections with more than two candidates, plurality voting is one of the worst methods. Candidates with overlapping constituencies often split votes, causing a less popular candidate to win. For example, Ralph Nader's third-party campaign helped Bush defeat Gore in 2000. With Nader and Bob Barr organizing to be on as many states' ballots as possible in 2008, such danger looms again.
In the following hypothetical situation with 100 voters, 73 percent agree that Hitler is the worst choice. (For simplicity, we limited possible rank orders to four.) But with plurality voting, he wins:
# Voters | Voted for | True preference (best> good> bad> worst) |
24 | Castro | Castro> Obama> McCain> Hitler |
26 | McCain | McCain> Obama> Castro> Hitler |
23 | Obama | Obama> Castro> McCain> Hitler |
27 | Hitler | Hitler> McCain> Obama> Castro |
Groups such as the FairVote Center for Voting and Democracy in Takoma Park, MD, advocate the Australian practice of instant-runoff voting (IRV). With IRV, voters rank the candidates explicitly. The candidate ranked first by the fewest voters is eliminated, and that candidate's votes transfer to the voters' second choices. This operation repeats until just one candidate remains. In the example, Castro wins after IRV eliminates Obama (whose votes transfer to Castro), then McCain (whose votes transfer to Castro, since Obama has already been eliminated), and finally Hitler.
But IRV can also produce illogical outcomes. Here, even though 53 percent of voters--a clear majority--prefer McCain over Castro, Castro still wins. (Fifty-three percent of voters also rank McCain ahead of Obama, and 73 percent rank him ahead of Hitler.) For mathematical reasons that are difficult to explain, IRV artificially favors extremist candidates. And IRV shares another problem with plurality voting: each can motivate voters to lie.
With plurality voting, if the Obama supporters strategically voted for Castro, Castro would win--an outcome they would prefer to a Hitler victory. With either IRV or plurality voting, McCain voters might be better off pretending their favorite was Obama, thus heading off a Hitler or Castro win. But with range voting, each voter can express how much (or little) he or she likes each candidate, and it is never rational to give your favorite less than the top score. (Assigning two or more candidates the same score is permitted.) Applying 0-to-99 range voting to the previous example, the votes might be:
# Voters | range votes |
24 | Castro-99 Obama-90 McCain-30 Hitler-0 |
26 | McCain-99 Obama-60 Castro-30 Hitler-0 |
23 | Obama-99 Castro-90 McCain-30 Hitler-0 |
27 | Hitler-99 McCain-0 Obama-0 Castro-0 |
Obama would win with 5,997, defeating Castro (5,226), McCain (3,984), and Hitler (2,673).
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e-voting election range voting voting machine voting technology