Range voting represents a variety of systems by which a voter may express a partial vote for a candidate, rather than a full vote. Where ranked voting allows a voter to move their vote onto a second choice in search of an electable, preferred candidate, range voting systems require rating candidates. In simplest form, the voter rates their top-ranked candidate as 1 and their lower-ranked candidates as less.
Range voting advocates suggest voting is about marginal utility, whereby voters seek to identify the most-useful candidate by rating how “good” they are and then adding up their scores. This contrasts with Condorcet voting, which seeks consensus on an overall-preferred candidate by rank.
Due to vote splitting, range voting simplifies to plurality: ratings depend on whether a third candidate appears strong or weak, rather than the marginal utility of a second-choice.
Plurality and the Split Vote
In a plurality system, voters elect by casting the most single votes for a candidate. When two desirable candidates exist, they may split the vote and elect a third candidate, as shown below.
In modern American elections, voters avoid casting a vote for a third party or even a weak candidate in a primary because they don’t want to throw their vote away. Knowing that Marshall is a strong candidate and Carter is the underdog, voters wishing to avoid electing Dark will vote for Marshall because a vote for Carter is a vote for Dark.
Ranked ballots allow voters to rank candidates in order, and so those five Carter voters may rank #1 Carter and #2 Marshall. Because all Carter voters also rank Marshall as preferred over Dark, the race between Marshall and Dark would reflect eleven votes for Marshall and eight for Dark. Marshall gets six votes against Carter’s five. Marshall thus beats Carter and Dark, and is the Condorcet Winner.
Without ranked ballots, voters must consider whether the popular candidate can clearly and strongly defeat the unpopular candidate, and whether they are for or against the popular candidate. Generally, the voter must vote for the most-popular candidate they find acceptable or they will weaken their chances.
Range Voting and the Split Vote
Range voting suffers an almost-identical defect. Consider the above race, where Marshall has a weak advantage over Dark, and Carter acts as a spoiler candidate.
A voter who prefers Carter over Marshall and considers Marshall half as good might rate the three candidates as follows:
Knowing that Marshall might just barely defeat Dark, however, the voter also knows that a half-vote for Marshall is a half-vote for Dark. Such ballots, with Marshall and Dark voters fully-committed, generate the following election results:
As such, Carter voters will want to increase the rating for Marshall, essentially diminishing their vote. By contrast, if Marshall and Carter are expected to come close to one another—say 8.5 and 9—and Dark is expected to lose, then Carter voters will want to rate Marshall lower to avoid electing Marshall when their first choice is Carter.
As with simple plurality voting, voters can more-freely vote for a third candidate when the opposition is expected to lose in any case. In such cases—such as where one party has a strong hold and all opposition parties are expected to receive far less than one-third of the vote—the choice often comes down to two candidates, and functions as a vote-for-one plurality vote: the voter’s best strategy is to rate their preferred candidate 1.0 and their lesser candidates as close to 0 as they feel confident in the capacity of the popular candidates to beat the unpopular ones regardless of any vote splitting.
Also as with simple plurality voting, voters must essentially sacrifice their third-party vote if they fear vote splitting. When rating a second-choice candidate, they must provide a high rating to avoid vote-splitting, and so increase the likelihood of electing that candidate.
The Not-So-Obvious Conclusion
Range voting systems behave little different than current plurality systems. In the most extreme cases, systems like STAR voting behave little different than California jungle primaries with instant run-off voting: split voting causes strategic voting, and the plurality winner becomes the majority winner.
Ranked voting systems provide voters the confidence in their vote: supporting a second-choice candidate does not harm their first-choice candidate, as an unranked candidate is only another type of lower-ranked candidate. Likewise, casting their first choice for a non-incumbent, non-popular candidate does not throw their vote away, as an utter loss simply moves the whole vote down. Ranked voting systems thus free the voter to seek a consensus vote through Condorcet voting rules, and better reflect the voter’s desires than range voting.