An SPD-led government may emerge after the recent elections in Germany

The Social Democratic Party of Germany (SPD) demonstrated the highest rate of support among German voters (25.7%) during the federal elections on September 26th. The CDU/CSU block is following closely (24.1%) but was unable to secure a leading position due to the changing leadership, as well as criticism of some recent policies.

These results make a coalition government necessary. As the Left received lower electoral support (4.9%) than predicted by the latest polls, the coalition of SPD, the Left, and the Greens cannot secure majority in parliament, thus, narrowing down the range of the possible outcomes of coalition formation. Moreover, the two leading parties, SPD and the CDU/CSU block, have indicated that they would not favor the so-called “grand coalition” (SPD-CDU/CSU).

We base our forecast on the election results, and assess the stability of alternative majority coalitions subject to compatibility constraints among their members. Specifically, we assume that no party besides the CDU/CSU would partner with the right-wing Alternative for Germany (AfD). We use the data from the Manifesto project to calculate the distance between the policy positions of the political parties.

We do not strictly exclude the possibility of SPD-CDU/CSU coalition but consider it a less likely scenario, as the data for the policy positions does not reflect the recent changes in leadership of the Union.


Constraints in coalition formation

Projected seats (bar size) vs. strategic influence (Shapley value) of political parties (red lines)
Stability (white bars) of predicted majority coalitions

Either CDU/CSU or SPD can join a coalition with FDP and the Greens as junior coalition partners. Out of these two, SDP-FDP-Green coalition has a greater stability (is more likely to form) due to a higher closeness of the platforms of these political parties.

This strategic situation grants FDP and the Greens a king-maker status: their choice of senior coalition partner may turn out decisive. CDU/CSU and SPD can escape this deadlock by forming a coalition together, where each party achieves a higher share of power than with FDP and the Greens, making this outcome possible, although less likely.