What is a vote? And aren't votes equal now?
Merriam-Webster defines a vote as “a usually formal expression of opinion or will in response to a proposed decision” - such as the election of a candidate to an office.
A voting method defines the boundaries of expression permitted in a vote and the counting system used to determine the election outcome.
When we vote today, our expression of opinion is limited to picking a single favorite, no matter how many candidates are running for an office. While this plurality voting method may sound equal, it is not. In the context of voting, the U.S. Supreme Court has declared that equality of voting - one person, one vote - means that the weight and worth of the citizens' votes as nearly as is practicable must be the same. Yet if we are limited to a single favorite, the system itself plays favorites, giving some voters an unfair advantage over others. Here's how:
When there are just two candidates in a race, each vote carries the same weight and so the outcome of the election reflects the will of the majority of voters. Every time there are more than two, however, candidates split votes:
Essentially, voters who prefer just one candidate have double the voting power or vote weight of those who prefer two candidates. The weight and worth of a voter's voice is thus entirely dependent on how many candidates with similar and opposing views choose to stand for office.
Because our power is inversely proportional to the number of candidates there are that we like, we are encouraged to choose the "Lesser Evil" rather than a longshot we might really like, and all but two polarizing candidates are discouraged from running for office.
The Equal Vote Coalition was founded in order to bring about the true equality in the vote that is our national birthright.
How can we tell definitively that a voting method provides an equal weight vote to the voters?
As it has been since ancient times, the test for equality of weight is balance. To determine whether two objects are of equal weight, they must balance when placed on opposite sides of a balance scale.
This very basic principle applies to voting methods. A voting method definitively provides votes of equal weight to all the voters if, and only if, for each possible vote expression that one voter may cast in an election, there exists another expression of the vote that another voter can cast that is in balance, such that the outcome of the election is the same whether both or neither votes are counted.
This test of balance provides the foundation for the Equality Criterion. A voting method passes the Equality Criterion if every possible vote expression has a counter-balancing vote expression and if the counting system produces the same election outcome when any pairing of a vote expression and its counter-balancing vote expression are added to the tally.
Which Voting Methods definitively provide an equal vote?
The traditional "Choose One Only" voting method, known as Plurality Voting doesn't provide an equal vote if there are over 2 candidates. Voters who have more candidates on their side are at a serious disadvantage because the ballot isn't able to express support for multiple candidates or show preference order between the candidates. This is why Plurality Voting is notorious for widespread vote splitting, spoiled elections, and for strongly incentivizing strategic voting.
There are a number of voting methods which employ a ranked ballot, but when people refer to Ranked Choice Voting they almost always mean the widely used Instant Runoff method (IRV). In IRV and other ranked ballot methods which don't require the voter to rank every candidate or which don't allow equal rankings, the ballot limitations and the voting rules themselves ensure that not all votes are equal. No matter the algorithm for computing the winner it is impossible to construct balancing votes for partial orderings of candidates unless candidates can be given equal rankings. Ranked Choice implementations that don't allow the voter to rank all the candidates, limiting rankings to 3rd or 4th choice can never satisfy this criterion, but these restrictions are the norm due to the logistical, practical, and technological constraints.
Even Ranked Choice systems that require the voter to provide full rank orderings, such that the voter could provide candidates in the opposite order of any other ordering, are not necessarily equal. IRV's counting algorithm, for example, discards the secondary choices of some of the voters, even those whose first choice has been eliminated. Thus the counting algorithm itself denies voters an equally weighted vote, whether or not the voter is required to rank every candidate.
An example of a Ranked Choice system that passes the Equality Criterion is the Borda Count method- when it's required that the voter rank every candidate.
In Scoring Systems, voters give each option an independent measure of value, like a rating, and each measure of value has a counterbalancing value: my yes to your no, or zero stars to your five. Scoring systems such as Score Voting and Approval Voting preserve the notion of equality of vote weight no matter how many candidates are in the race.