The unicameral system and the electoral system of proportional representation have allowed almost exact equality in proportional representation among the constituencies on the national level and has produced a multi-party system. The constitution requires, however, that a party must gain at least 4% of the national popular vote or 12% in a constituency to be represented in the Riksdag. Sweden has for many years utilized the party list system in which the candidates for office from any given party are listed in order of party preference. If a party won ten seats in the Riksdag, the top 10 candidates from that party would be represented in parliament. In 1998, voters for the first time had the option of indicating which candidates on the party list whom they preferred to see elected to parliament and to local councils. A given candidate must receive at least 8% of his or her party's ballots in any electoral district to be moved to the top of the party's nomination list. If no candidate attains the 8% threshold, the party's nomination list remains in force.
Sweden had a stable party system until the end of the 1980s. The parties of the political right include the Moderate (formerly Conservative) Party (Moderata Samlingspartiet, M), which favors tax reform and trimming the welfare state; the Liberal Party (Folkpartiet Liberalerna, FP), which is a traditional European liberal party; and the Center (formerly Agrarian) Party (Centerpartiet, C), which has in the past represented rural interests and has tried to refashion itself as an "alternative" centrist party favoring environmental issues. The left side of the Swedish political spectrum includes the dominant Social Democratic Party (Socialdemokratiska Arbetarepartiet, S), which is responsible for creating the welfare state and which gets considerable support from organized labor in Sweden; and the Left (formerly Communist Left) Party (Vänsterpartiet, V), which has distanced itself from its communist past and now advocates positions that champion gender equality and attracts voters that are wary of the Social Democrats' move toward the center. In 1988, the environmentalist Green Party (Miljöpartiet de Gröna, MP) joined the long-standing parties on the left represented in the Riksdag. In the 1991 election, two new parties emerged on the right, the Christian Democrats (Kristdemokraterna, KD) and the New Democracy Party (Ny Demokratiska, NyD).
Except for a brief period in 1936, the Social Democratic Labor Party was in power almost uninterruptedly from 1932 to 1976, either alone or in coalition. In 1945, the Social Democrats dissolved the wartime Grand Coalition Cabinet representing every party except the Left Party Communists and launched a program of social reform. Although inflation and other difficulties slowed the Social Democratic program, steadily mounting production encouraged the government to push through its huge social welfare program, which was sanctioned in principle by all major parties.
The Social Democrats held or controlled all parliamentary majorities until the elections of September 1976 when a non-Socialist coalition including the Center Party, the Moderates, and the Liberals won 180 of the 349 seats at stake. The center-right coalition retained control in the 1979 election with a reduced majority of 175 seats and a stronger showing for the Moderates. In the election on 19 September 1982, however, the Social Democrats returned to power. Olof Palme, who had been the Social Democratic prime minister from 1969 to 1976, was able to put together a new coalition cabinet on 8 October 1982. His party remained in power, though with a reduction of seats, following the 1985 election. Palme was assassinated in February 1986; he was succeeded by Ingvar Carlsson.
The 1988 election was a watershed that registered political discontentment. The Social Democrats lost seats as the Moderates' and Liberals' share of the vote continued to increase. More remarkably, for the first time in 70 years, a new party gained representation in the Riksdag—the Green Party (MP), which obtained 20 seats. The Social Democrats were narrowly defeated in September 1991, and the government of Ingvar Carlsson gave way to that of Carl Bildt (Moderate Party), who headed a minority four-party, center-right coalition composed of the Moderates, the Liberals, the Center Party, and the Christian Democratic party, which together controlled 170 seats.
The 1991 election represented a gain for two previously unrepresented parties—Christian Democrats (26 seats) and New Democracy (25 seats)—who managed to exceed the 4% threshold while the Greens fell below the threshold and lost representation in the Riksdag. New Democracy emerged prior to the 1991 general election as a party of discontent urging tax cuts and reduced immigration. The Left Party-Communists were renamed the Left Party (VP) in 1990.
The Moderate Coalition, which promised to end Sweden's deepening recession, found itself unable to address the country's problems, largely because of Social Democrat and popular opposition to its cost-cutting measures. In 1994, the Social Democrats were returned to office by a population reluctantly willing to bear austerity if initiated and directed by the party that created the welfare state. The Social Democratic Coalition government under Prime Minister Ingvar Carlsson navigated Sweden through the referendum on Swedish membership into the EU in late 1994. Carlsson was replaced as prime minister by the former Finance Minister, Göran Persson.
The September 1998 election represents a protest vote against the mainstream parties and perhaps greater voter polarization in Sweden. The mainstream party of the left, the Social Democrats, had their worst election showing in over 70 years but maintained power in a minority government dependent upon support from a formal alliance from the Left and Green parties. The Social Democrats slipped from 45.3% of the vote in 1994 to 36.4% in 1998, while the Left Party advanced from 6.2% in 1994 to 12% in 1998 and the Greens returned to the Riksdag with 4.5% of the national vote. Similarly on the right, the Christian Democrats advanced from 4.1% of vote in 1994 to 11.8% in 1998 at the expense of the more centrist Center and Liberal parties, which narrowly passed the 4% threshold. The Moderates' share of the vote held basically steady.
Much of this discontent in the 1998 election was attributed to the budget tightening process that resulted in major cutbacks in social welfare benefits. A growing level of public distrust of politicians was fueled by prominent scandals of misuse of public funds. The reform to allow voters to select individual candidates does not seem to have diminished the distance between voters and elected representatives as only 29.9% took advantage of the opportunity to do so at the national level.
The 2002 general elections campaign focused largely on the issues of immigration and membership in the euro zone. The Liberals and Moderates supported a plan to import large numbers of guest workers, who would be classed as non-citizens. The Social Democrats and the Left Party denounced this plan. The Social Democrats registered a strong showing in the elections, winning 39.8% of the vote (up from 36.4% in 1998) and taking 144 of 349 seats in the Riksdag. The Social Democrats under Göran Persson formed a government with the Left Party(8.3% of the vote and 30 seats), and the Greens (4.6% and 17 seats). However, the Liberal Party, with its immigration plan, increased its strength in parliament, with 13.3% of the vote (up from 4.7% in 1998) and 48 seats. The Christian Democrats fell from 11.8% in 1998 to 9.1% of the vote in 2002 (33 seats). The Moderates (15.2% of the vote and 55 seats) and the Social Democrats support a "yes" vote in the upcoming referendum on joining the euro zone to be held in September 2003.