The Greens did very well in the EU elections. One interpretation is that a substantial minority of Europeans are now seriously focused on climate issues and voted Green to promote EU-wide climate policies.

But the Greens also stand for pan-Europeanism, multiculturalism, civil liberties, and the rule of law; and they have a specific demographic base. They are challenging or even replacing social democrats as a pillar of the center-left, without expanding the total center-left vote by much (if at all). It is not clear that they have a stronger policy platform on climate issues than the socialist parties in countries like Germany.

Therefore, a different interpretation is plausible. Perhaps the social democrats have fractured along class lines, and the Greens have taken away their college-educated vote, not because of climate but because of a whole basket of issues and values.

To explore that second hypothesis, I’ll focus on Germany–the birthplace of social democracy (in 1875) and the EU’s most important economy. There, the Social Democratic Party (SDP) came in third with less than 16%, surpassed by the Greens at 20.5%.

The SPD was traditionally a coalition of unionized industrial workers plus college-educated employees who were close to the welfare state (teachers, civil servants, and the like). These were the groups that stood to benefit most from an active state, and they were effectively organized in unions, professional associations, and the SDP itself. In other words, they didn’t just have votes but also organizational muscle. They played a major role in building the welfare state.

However, at least some of the party’s white-collar base has migrated to the Greens, who have become less environmentalist and more of a socially-liberal, cosmopolitan, center-left party. And some of the industrial workers have left the SPD for the right. The net result is a weakening of the organized center-left. Yes, the Greens are flourishing, but that is mostly at the expense of the SDP and reflects a fracturing of the social democratic coalition that helped to build the Federal Republic.

An EU election can be misleading if you want to understand the deeper state of a country’s politics. Only about 60% of eligible Germans voted this week, and they presumably focused more than usual on European issues. They certainly opted more than usual for small parties. Therefore, as second graph, I show how the whole German adult population responded when asked which party they felt closest to in 2016:

These data are now two years out of date but probably reflect the underlying conditions. The order is still the familiar one–Christian Democrats, Social Democrats, Greens, and then others–but the once-mighty SDP is already down to 26.2% in this survey. Left parties claim 58.7% of the total electorate but stand very far apart on issues. The traditional establishment parties (Christian Democrats, Social Democrats, and Liberal Democrats or FDP) claim just 64.2% of the vote in total. Both the left and the center are larger than the right, but the center-left is far from dominant.

This third graph shows how this pattern had evolved since 2002:

The change in the position of the Christian Democrats has not actually been huge. They have certainly seen some erosion since the immigration crisis, but they are only six points less popular than they were in 2002. The Greens stand not far from where they were in 2002, but they temporarily improved their position while the Social Democrats were sustaining their largest decline (2006-10). The right also rose, but mostly after the SDP had seen its major losses (2012-16).

That graph is consistent with the theory of a fragmenting SDP. However, trends in party support do not tell you how individuals shifted. Maybe the Greens grew by attracting former SDP members, but maybe those two lines converged for other reasons. The Greens declined and the right-wing grew after 2010, but we don’t assume that Green Party members defected all the way to the right.

As an imperfect test of the thesis that the SDP has indeed lost members to the Greens and the right, I graphed party support by income band for three selected years. I am assuming that if the SDP falls and the Greens or the right-wing rises within a specific income stratum, then people are actually changing their party affiliations in that way.

In 2002, the SDP performed best at three levels: the poor (who might benefit most from welfare), the fourth and fifth deciles (which may reflect unionized industrial workers), and the 8th and 9th deciles (where people with a lot of education may land). The Christian Democrats dominated among the rich but drew votes from across the spectrum. The Greens could not yet be described as an affluent party. Also (not shown here) they performed worse than the SPD among students. The right drew strongest from the lower-middle class.

By 2010, the Greens were more affluent and the SPD had lost a substantial amount of support in the upper deciles. The Greens were now also running even with the SPD among current students. The far right was weaker than it was in 2002, but I think that reflected a temporary change in the array of parties. The left drew support almost entirely from the lower income bands.

And by 2016, the right was much stronger–in third place in some of the lower income bands, behind only the SDP and Christian Democrats. Meanwhile, the Greens had become distinctly affluent and (again not shown here) they dominated the current student vote. They lost support only in the top income range, where the Christian Democrats were still ahead (although less so than in 2002).

These patterns are not sharp and dramatic; there is actually a fair amount of stability despite tumultuous times. But it does look as if the SDP has lost members to the Greens over lifestyle issues, and to the right because of nationalism.

The SDP and the Greens can certainly come together again in parliamentary coalitions, but at the grassroots, the coalition that sustained the German welfare state looks weaker than it was for decades. Also, I am not sure the Greens have the organizational muscle that the SPD had in its heyday, which means that their capacity to implement policy may be weaker.

If you care about environmental policy and social justice, you have to welcome the Greens. But the question is whether the center-left as a whole has sufficient capacity to govern.