2010 Riksdag Election — Sweden Democrats Enter Parliament
On 19 September 2010 the Sweden Democrats won 5.7 % of the vote and 20 seats, breaking the 4 % threshold for the first time and forcing the re-elected Reinfeldt Alliance into minority government — the moment Sweden's postwar two-bloc majority arithmetic broke down for good.
The 19 September 2010 Riksdag election did two things at once. It re-elected Fredrik Reinfeldt’s Moderate-led Alliance, the first non-socialist bloc to win consecutive elections since 1928. And it sent the Sweden Democrats across the 4 % threshold with 5.7 % and 20 seats — the first time a nationalist-right party had entered the Riksdag in the modern era.
The arithmetic snapped immediately. Without an outright majority and with both blocs publicly committed to excluding SD, Reinfeldt II had to govern as a minority cabinet that could lose any non-budget vote where the opposition and SD aligned. The cordon sanitaire became the constitutional fact of Swedish politics on the night of the election — and stayed there for at least a decade.
The 2010 vote is the structural origin point of everything that follows: the 2011 cross-bloc migration deal, the 2014 December Agreement, the 2019 January Agreement, and ultimately the right-wing realignment of the 2022 Tidö Agreement. Every government formed in 2014, 2018, 2021 and 2022 is a reply to the seat distribution announced this evening.