Social Democrats win power in Sweden

Fredrik Reinfeldt has announced his resignation as Prime Minister of Sweden and leader of the Conservative party after having taken a severe beating in Sunday's general election, whose only real winner is the right-wing extremist party the Sweden Democrats. The Speaker of Parliament will ask the leader of the Social Democrats, Stefan Löfven, to form a new government.
Given the election results, Löfven's task will not be an easy one. His party won 31.2 %, a gain of only 0.4 % from its result in the 2010 election, which was its worst since 1911. His prospetive coalition partner, the Green Party, won 6.8 % of the votes, back 0.4 % from 2010, while the third party of the left, the Left Party, gained 0.1 % and achieved 5.7 %. Thus the left wing's total gain was a mere 0.1 %.
Yet the left wins power as all of the four parties which have governed Sweden since 2006 lost support. The Conservative party backed no less than 6.7 %, winning only 23.2 % of the votes. The Liberal People's Party received 5.4 % (-1.7), the Christian Democrats 4.6 % (-1 %) and the Centre Party 6.1 % (-0.4 %).
What is lost by the four governing parties is won by the Sweden Democrats, who achieved 12.9 %, a gain of 7.2 %. The Sweden Democrats thus hold the parliamentary balance, but all the other parties have made it clear that they will under no circumstances co-operate with the extremists, whose roots lie in Nazism.
This creates a very difficult parliamentary situation, as the new government, which is widely expected to consist of the Social Democrats and the Green Party, will not be able to form a majority with neither the Left Party nor the Centre Party nor the Liberal People's Party. Indeed the support of either the Left Party and the Centre Party or the Left Party and the Liberal People's Party or the Centre Party and the Liberal People's Party will be needed, but the Centre Party and the Liberal People's Party have made it clear that they will not support a Social Democratic government. However, if the "established" parties are to continue to isolate the Sweden Democrats, some sort of co-operation across the line that divides the two blocks will be necessary.
If Stefan Löfven, a former trade union boss who has until now never been an MP or a minister, succeeds in forming a coalition with the Green Party it will be the first time that party enters government and the first time since the 1950s that the Social Democrats govern with another party. Another option is that the Social Democrats form a government alone, but dependent of support from some of the smaller parties.
There is also a theoretical possibility that an impossible parliamentary situation may lead to Parliament being dissolved and an extra election called before 2018, but this has not happened after the introduction of the new Constitution in 1974.