Different uses for voting need different types of voting.
Manipulation of Elections
This page deals only with the manipulation of voting rules. It does not look at manipulation of news events or control of news corporations, funding or truthfulness of campaign ads, intimidation or buying of voters, and tampering with ballot boxes or voting machines. Those can block democracy regardless of voting rules. Yet rules that offer few opportunities for rule manipulation improve the chances of democratic results.
What's wrong with the common election rules? For one thing, they are inherently erratic in their results and that is closely related to some types of manipulation. Each voter gets one vote under the simplest plurality rule, or a number of votes equal to the number of seats to be filled under the bloc vote rule. The candidates that get the most votes win.
This usually elects people to represent the plurality or largest group. (Two other plurality rules are also erratic, but semi-proportional; they often elect a few minority reps. Limited vote gives each voter fewer votes than the number of seats. Cumulative vote lets each voter give more than one vote to the same candidate.)
All plurality rules reward finding opportunities to cast a deciding vote, the one vote needed to make a loser win with no votes to spare. Votes that do not help build exactly enough support for a win are called wasted votes. Excess votes for a winner are just as useless as votes for a loser. Neither will affect representation on the council. (What are your chances of casting a deciding vote?)
Manipulations Before VotingDivide and Conquer: Plurality rules are erratic because the number of votes an option gets depends more on the number of similar options than on the number of people who support such options. (If voters have a choice of several liberals and one conservative, who is most likely to win?) So, encourage your rivals to nominate candidates, lots and lots of them.
Gerrymander involves drawing many one seat districts where we win with 51% and a few where they win with much more than 51%. That means many of their votes are wasted. (Similar tactics work under the bloc vote rule.) According to the non-partisan Center for Voting and Democracy "redistricting is quite simply a process in which legislators choose their constituents before their constituents choose them." Encourage rivals to nominate only one candidate so she wins with excess votes, all wasted. Multi-winner elections under Proportional Representation make gerrymanders much less effective. These rules put an end to divide and conquer.
Manipulations By Voters
Here's how to take advantage of multi-winner plurality rules such as bloc vote:
Start by making the list shorter. Cross off any candidates you don't like. Obviously you don't want to cast a vote for one of these follies. Cross off candidates that seem to have very little chance. Any vote for them is a wasted vote because it does not help build the support required for a winner. Even your most preferred candidate should get no vote if her chance of winning is small. (That last strategy is called “decapitation”.)
Free rides: In multi-winner races, don't vote for a person (or project) who has lots of support. She doesn't need yours. Save your vote(s) for candidates where you can make a difference. Of course, when many people take free rides, even the best candidates can lose.
Yes-no ballots promote manipulation which leads to cynicism.
Most point voting rules offer two easy strategies:
Punishing votes: Give the minimum to any candidates you don't like, or that rival and threaten your favorite. This is often true even if the rival is your second favorite. Sometimes called “burying,” it is substantially the same as “raising turkeys”, giving high ranks to hopeless losers.
Exaggerations: Give the maximum allowed to the favorite candidate who seems to have a good chance of winning.
The chapter on legislative voting will look briefly at agenda manipulations. Another page in that chapter will explain why the hardest rule to fool is often Instant Runoff Voting, also known as Alternative Vote or Single Transferable Vote.
These voting strategies are less effective at manipulating the Condorcet, STV, or ensemble rules explained in the following chapters. Most readings in the resources page will explain other serious defects in plurality rules.
Changing a voting rule may seem a risky step. But the IRV and Condorcet rules have been tested for 100 years. Now computers make them easy to tally. The greater risk is continuing to use ancient rules that make democracy work poorly.
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