The first day of the investiture debate in the Spanish parliament’s lower chamber in Madrid on Monday. Acting prime minister Pedro Sánchez could be elected prime minister if a deal with left-wing coalition Unidas Podemos is reached. (Zipi/EPA-EFE/Shutterstock)

Coalition governments are a common electoral outcome in many parts of the world. Both large and small parties have a chance to participate in government and hold important ministerial positions.

But is there a downside to being a coalition partner? Take a look at recent election results in Europe. After the 2017 German elections, the Social Democratic party (SPD) — one of the two largest parties in Germany — saw its vote share drop to the lowest in decades. In the European Parliament elections, the SPD came in a distant third with only 15.8 percent of the vote.

In the Danish elections in June, the Liberal Alliance’s (LA) vote share dropped from the previous election. The party experienced a relative loss of nearly 70 percent in voter support.

These are two parties of different sizes and ideologies — but here’s what they have in common. Both parties served as junior coalition partners in the incumbent government.

In our forthcoming article in the Journal of Politics, we show that a party that doesn’t hold the prime ministership may suffer in the next election because it joined a coalition government. This isn’t a phenomenon that is unique to German or Danish politics — it’s a general trend across Europe. Based on a comprehensive comparative analysis of 219 elections in 28 European countries from 1972 to 2017, we find that junior coalition partners suffer dramatic electoral losses. Overall, junior partners lose an average of 17 percent of the vote in the next election, compared to senior partners.

Why does this happen?

One reason is that junior partners cannot enact much of what they promised before the election. To govern, they must compromise with their senior partners. Although they campaigned on specific policies, they often may not be able to implement them. For example, the most important policy promise the German Free Democrats (FDP) advocated during the 2009 election campaign was a major reform of the German tax system. This tax reform was never enacted.

But there’s another reason. Junior partners often can’t sufficiently differentiate themselves from their larger coalition partner. This means that voters cannot distinguish between the policy profile of the prime minister’s party and the policy positions of its junior coalition partners. Even though junior parties typically pursue their own distinct policy goals, they don’t always succeed in communicating their policy stances. Voters see little difference between junior and senior partners — and thus see no reason to vote for the junior, less powerful party in the next election.

Both of these explanations demonstrate that what’s good for governing — consensus and compromise — is not necessarily good for subsequently attracting votes.

So what’s a potential coalition party to do? This conundrum is even more problematic because we find that parties that stay in the opposition do better electorally than those that join as junior partners. On average, opposition parties gain 3 percent more votes than junior coalition parties in the next election. No surprise here — more and more parties thus are reluctant to join coalition cabinets as junior parties, since they fear dramatic electoral losses lie ahead.

Here’s why this finding matters

First, this makes government formation increasingly difficult. And the process can take much longer than it did in the past. Traditional coalition partnerships may no longer seem viable because of these potential vote losses. Moreover, these potential junior coalition parties increasingly realize that holding executive office may not be helpful in winning votes. This can make coalition negotiations a long and hard sell.

Here are a couple examples. Following the 2017 elections, German Chancellor Angela Merkel and her Christian Democrats (CDU/CSU) had a very hard time forming a government, as both the SPD and the Free Democrats (FDP) — both of which had governed with the CDU/CSU previously, from 2009 to 2013 — were reluctant to join another coalition cabinet because they had lost votes in the 2013 elections. It took nearly six months of intensive negotiations — during which time Germany was essentially without an elected government — before the SPD reluctantly joined a coalition, after coalition talks with the FDP had failed. In Denmark, the government formation process following the recent June elections took three weeks, the longest in over 30 years.

Second, smaller parties may opt out of a coalition, and instead stay in the opposition. This may influence how the voters of these parties are represented — parties essentially choose to stay in the opposition rather than risk being voted out later, as penalty for being a junior coalition partner. This is indeed what happened to the FDP in 2013, when it was kicked out of parliament because it did not receive enough votes to cross the threshold.

All of this means that potential junior partners will have to seriously weigh the costs and benefits of joining a coalition. As we show, staying in the opposition may be a better strategy than the power and prestige of joining a government.

As established parties increasingly steer clear of the risk of future electoral losses, we may see populist and extremist parties offered a chance to join coalition governments as party systems become more fragmented and large parties cannot govern alone.

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Heike Klüver is a professor and chair of Comparative Political Behavior at Humboldt-Universität zu Berlin. Follow her on Twitter @HeikeKluever.

Jae-Jae Spoon is a political science professor and director of the European Studies Center at the University of Pittsburgh. Follow her on Twitter @JaeJaeSpoon.