The SPD won only 37.1 percent of the votes in North Rhine and Westphalia, down 5.7 points since the last state election five years ago.
The Greens, the SPD’s coalition partners in the state assembly, received 6.2 percent of the vote, down 0.9 percent.
The conservative Christian Democratic Union won the largest share of the vote, with 44.8 percent — up 7.8 percent.
The SPD had ruled in the state capital Düsseldorf for 39 years. For many years, the SPD was able to achieve an absolute majority in the Ruhr, the former heartland of steel and coal production, in which five million people still live.
This concentration of production meant that from the 1950s onwards this region was the real heartland of the SPD.
The SPD vote two weeks ago represents the party’s worst result in a state election since 1954. Only one in five voted for the SPD.
In state elections held in 1985 and 1990, the SPD had been able to win over 50 percent of the votes cast.
Analysis of the results shows that the SPD suffered losses particularly among its traditional supporters.
It lost about 9 percent of votes among workers and union members. It also lost some 8 percent of support among voters aged 30 to 44.
In total, the SPD received 3.1 million votes. This represents a loss of some 40 percent from the 1998 Bundestag election when the SPD won just over five million votes in the region.