The Chilean Congress is bicameral, comprised of a Chamber of Deputies as the lower house, whose members serve four-year terms, and a Senate as the upper house, whose members serve for eight years. The 120 seats in the lower house are directly elected using an open-list PR system, but an usual and distinguishing feature of the Chilean system is that all seats are elected from two-member districts, which makes it more difficult for small parties to gain representation on their own.
Parties, or coalitions of parties, present a list of two candidates, and voters indicate a preference for one candidate within one of the lists. The votes of both candidates on each list are totaled first, then the two seats are allocated. The first seat is awarded to the most popular candidate from the list with the most votes; then that list's vote total is divided by two. If this number is still higher than any other list's total of votes, the second candidate gets the second seat. Otherwise, the second seat goes to the candidate with the most personal votes from the second-placed coalition's list.
This two-member PR system was designed in 1989 by the outgoing military regime of General Augusto Pinochet. The stated goal was to encourage broad cross-partisan coalitions and discourage the representation of small parties, particularly the Communists, who had thrived under Chile's more permissive PR system, which utilised larger multi-member districts, up to 1973. On this count, the system appears to be working. Parties can win representation in Congress only if they are part of one of the two largest lists in a given district. Those parties on the radical left that have been unwilling or unwelcome to enter the centre-left Concertación coalition have been virtually disenfranchised, winning no seats and watching their vote share drop from 11 percent to six percent in the two elections since redemocratization.
The incentive that this electoral system gives to form coalitions has carried over from the electoral arena to government, and is so formidable that Chile's traditional multi-party system now performs very much like a two-party system. Although parties remain organizationally distinct and candidates bear party labels on ballots, these labels have effectively been superseded by coalition labels. Coalition leaders negotiate candidate nominations jointly and can impose discipline across all members of the coalition. The result is that the Chilean Congress has come to be organized around two major coalitions that are more stable than was previously the case in Chile's fluid multi-party system.
A second important effect of the system is that, given the distribution of electoral support in Chile, elections systematically over-represent the coalition of the right, the Unión Para Progreso (UPP). The system ensures that in every district, the top two coalition lists will win equal representation unless the top list more than doubles the vote total of the second-placed list. This too is the result of a conscious choice by system designers. Based on the results of a 1988 plebiscite as well as previous elections, the military regime knew its supporters were a minority in almost every region of the country, but that its support was consistently in the range of 30 to 40 percent, whereas the Concertación had majority support and intended to sustain their coalition. The Chilean electoral system is unique in its tendency to over-represent second-place finishers; and indeed in both the 1989 and 1993 elections the UPP has won a six to seven percent greater share of seats than its proportional share of the vote.
The Concertación has expressed a desire to increase the number of deputies elected from each district, thus making the system more proportional. However, all changes have been steadfastly opposed by the UPP and the appointed senators who, together, hold a majority in the Senate. As the system enters its third electoral cycle in 1997, the electoral interests of all parties that have succeeded under these rules may progressively undermine support for radical reform.
