Bloc voting (or block voting) (also called at-large voting, in reference to Plurality-at-large) refers to a class of Multi-Member System which can be used to elect several representatives from a single constituency.
- Bloc Approval Voting: Each voter chooses (no ranking) as many candidates as desired. Only one vote is allowed per candidate. Voters may not vote more than once for any one candidate. Add all the votes. Elect the candidates with the most votes until all positions are filled.
- Bloc Plurality Voting: Each voter chooses as many candidates as there are seats to be elected. Add all the votes. Elect the candidates with the most votes until all positions are filled.
- Bloc Score Voting: Each voter scores all the candidates on a scale with three or more units. Starting the scale at zero is preferable. Add all the scores. Elect the candidates with the highest total score until all positions are filled.
- Bloc STAR Voting: Each voter scores all the candidates on a scale from 0-5. All the scores are added and the two highest scoring candidates advance to an automatic runoff. The finalist who was preferred by (scored higher by) more voters wins the first seat. The next two highest scoring candidates then runoff, with the finalist preferred by more voters winning the next seat. This process continues until all positions are filled.
- Cumulative Voting: In this system, a voter facing multiple choices is given X number of points. The voter can then assign his points to one or more of the choices, thus enabling one to weight one's vote if desired. This could be achieved through a normalized ratings ballot, or through multiple plurality ballots, one per each point allocated. Typically, each voter will have as many votes as there are winners to be selected. It is equivalent to doing SNTV but allowing the voter to split their vote up into fractions between various candidates.
- Single non-transferable vote: Each voter casts one vote for one candidate in a multi-candidate race for multiple offices. Note that this is very different from most bloc voting methods in that it passes a weak form of PSC.
In Bloc Plurality voting, also known as Plurality-at-large voting, each voter places n Xs on the ballot paper, where n is the number of candidates to be elected. The n candidates with the highest number of votes are elected.
The bloc voting system has a number of features which can make it unrepresentative of the voters' intentions. It regularly produces complete landslide majorities for the group of candidates with the highest level of support, though this does tend to lead to greater agreement among those elected. Like first past the post methods, small cohesive groups of voters can overpower larger numbers of disorganised voters who do not engage in tactical voting.
Bloc voting has its origins in common law. It was used in the Australian Senate from 1901 to 1948 (from 1918, this was preferential bloc voting), is widely used for local elections in the United Kingdom and is often used to elect the boards of directors of corporations.
Partial block voting (or Limited-voting) involves each voter receiving fewer votes than the number of candidates to be elected. This can enable reasonably sized minorities to achieve some representation. It is used for elections in Gibraltar, where each voter has 8 votes, and 15 seats are open for election: the usual result is that the most popular party wins 8 seats and forms the Gibraltar administration, while the second most popular wins 7 seats and forms the opposition. If each voter only receives one vote then partial bloc voting reduces to a single non-transferable vote.
In preferential bloc voting, which is the bloc form of IRV, each voter ranks the candidates (i.e. places the numbers 1... x on the ballot paper (where "x" is the number of candidates on the ballot paper)). Candidates with the smallest tally of first preference votes are eliminated (and their votes transferred) until a candidate has more than half the vote. The system is re-started n times with the elected candidates removed and all votes returning to full value.
In general, Bloc methods can be summarized as electing the top n ranked candidates of some single-winner voting method.
Block voting also describes a system of winner takes all decision-taking whereby the vote of an entire electoral unit is cast in line with the majority decision of that unit (i.e. discounting any contrary votes). This is the system used by most States for the U.S. Electoral College. It is also used in the UK by the Trades Union Congress; in a irony of history, it was introduced in 1895 by supporters of the Liberal Party to prevent or delay the establishment of the Labour Party, and it took the Labour Party from 1900 until 1993 to remove it from its own structures.
It is generally possible to make a majoritarian or utilitarian Bloc voting method at least semi-proportional by sequentially 1) electing the best candidate according to the Bloc method and 2) deweighting the ballots that supported that candidate to some extent.