Block plurality voting
Plurality block voting is a non-proportional voting system for electing representatives in multi-winner elections. Each voter may cast as many votes as the number of seats to be filled.[1] The usual result when the candidates divide into parties is that the most popular party in the district sees its full slate of candidates elected in a seemingly landslide victory.
The term "plurality at-large" is in common usage in elections for representative members of a body who are elected or appointed to represent the whole membership of the body (for example, a city, state or province, nation, club or association). Where the system is used in a territory divided into multi-member electoral districts the system is commonly referred to as "block voting" or the "bloc vote". These systems are usually based on a single round of voting.
The party-list version of plurality block voting is party block voting (PBV), also called the general ticket, which also uses a simple plurality election in multi-member districts. In such a system, each party puts forward a slate of candidates, a voter casts just one vote, and the party winning a plurality of votes sees its whole slate elected, winning all the seats.
Casting and counting ballots[edit]
Block voting[edit]
In a block voting election, all candidates run against each other for m number of positions, where m is commonly called the district magnitude. Each voter selects up to m candidates on the ballot. Each of the voters have m votes, and are able to cast no more than one per candidate. They cannot vote for the same candidate more than once, as is permitted in cumulative voting.[2]
Voters are permitted to cast their votes across candidates of different parties (ticket splitting).[3]
The m candidates with the most votes (who may or may not obtain a majority of available votes or support from the majority of the voters) are declared elected and will fill the positions.
Due to multiple voting, when a party runs more than one candidate, it is impossible to know if the party had support of as many voters as the party tally of votes (up to number of voters participating in the election) or if it had support of just the number of voters equivalent to the votes received by the most popular candidate and the other candidates of that party merely received votes from subset of that group.
Example[edit]
Candidates are running in a three-member district; each of the 10,000 voters may cast three votes (but do not have to). Voters may not cast more than one vote for a single candidate.
Party A has about 35% support among the electorate, Party B around 25% and the remaining voters primarily support independent candidates.
Candidates of Party A won in a landslide, even though they only received a plurality (35–37%) among the voters (10,000). This is because most parties run as many candidates as there are open seats and voters of a party usually do not split their ticket, but vote for all candidates of that party.
By contrast, a single transferable vote system would likely elect 1 candidate from party A, 1 candidate from party B and 1 independent candidate in this scenario.
Compared to preferential block voting[edit]
Block voting, or plurality block voting, is often compared with preferential block voting as both systems tend to produce landslide victories for similar candidates. Instead of a series of checkboxes, preferential block voting uses a preferential ballot. A slate of clones of the top preferred candidate will win every seat under both systems, however in preferential block voting this is instead the instant-runoff winner.
Vacancies[edit]
In Brazil, where Senatorial elections alternate between FPTP and block voting, each main candidate is registered along with two substitutes. Votes in either election are cast and counted based on these three-candidate slates; when a Senator leaves office before their eight-year term ends, the first substitute takes their place, and then the second if needed.
On the other hand, in political systems with a culture of by-elections, filling vacancies under Block Voting can be harder than in other voting methods. This is because by-elections to fill a single seat in a multi-member district can be expensive.
There are alternative ways of selecting a replacement in such systems: one way is to fill any seat that becomes empty by appointing the most popular unsuccessful candidate in the last election, i.e. a countback. This was used in the City of Edmonton (Canada) following the 1905 Edmonton municipal election.[5]