Why did the Social Democratic Party of Germany receive its worst postwar result in the 2017 general election?

In the September 2017 general election, the Social Democratic Party of Germany (SPD) received 20 percent of the vote, marking its worst performance in the postwar era.1

This decline in support was attributed to several factors:

• Participation in the Grand Coalition: The party’s involvement in the "grand coalition" with the Christian Democratic Union–Christian Social Union (CDU-CSU) alliance did not bolster the SPD's popularity.1
• Rise of Minor Parties: Amidst a period of steady economic growth, minor parties saw their support increase as voters sought alternatives.1
• Social and Political Climate: The party faced challenges from rising anti-immigrant sentiment within the country.1

Following the election, despite party leader Martin Schulz initially vowing that the SPD would not participate in another grand coalition, the party ultimately reversed this pledge after months of failed talks and the prospect of fresh elections.1