BAVARIA’s conservative Christian Social Union (CSU) has spent the past months performing a sort of controlled experiment into the state of European politics today. In one of the wealthiest parts of Europe, where unemployment barely exists and the migration crisis of 2015 was handled remarkably well, the party that had governed for decades lurched far to the right over the past half-year. The CSU is the sister party of Angela Merkel’s more moderate Christian Democratic Union (CDU), which runs candidates in the other 15 German federal states but not Bavaria. Horst Seehofer, federal interior minister in the CDU/CSU’s coalition with the centre-left Social Democrats (SPD), has spent the past months pushing Mrs Merkel’s government to the brink of collapse over migration and related issues. In Bavaria Markus Söder, his successor as state premier, has pursued a quasi-Trumpist strategy focused on the restoration of Bavaria’s “Christian” identity.

This strategy hit the buffers with a deafening crash on Sunday when Bavaria went to the polls in its five-yearly state election. Last time, in 2013, the CSU regained its majority in the state parliament after its first period in coalition since its rise to prominence in the 1950s. But with party leaders panicking after the CDU/CSU’s poor result in last September’s national election, at which the far-right Alternative for Germany (AfD) took third place, it attempted to emulate elements of the AfD’s strategy. Today it paid the price: its support falling from 48% in 2013 to 37% (according to the latest prognosis) as voters turned instead to the left-liberal Greens, the rightish-localist Free Voters (FW) and the AfD.

That was marginally better than the gloomiest polls had suggested but still abysmal by CSU standards. The first prognosis at 6pm local time had been even lower, the crowd at the CSU rally at the Bavarian state parliament in Munich standing silent, but for a few mutters, as it was read out on the giant screen before them. Shortly afterwards I ran into Mr Söder as he entered the building and asked if he felt relieved. He grimaced and said he needed to speak to colleagues. A while later, speaking before the CSU rally, he claimed a mandate to form a government—but appeared brow-beaten and chastened, acknowledging that the party needed to reflect on the result. Heads may yet roll in the CSU. Meanwhile the Green Party rally, also held within the magnificent Maximilianeum building in Munich housing the Bavarian parliament, was abuzz. The Greens—now in second-place nationally in several polls thanks to a newly pragmatic, centrist pitch that worked wonders in Bavaria today—feel they have the momentum.

What is the significance of tonight’s result? In Bavaria it may well mean a CSU-FW coalition and a change of personnel at the top of the CSU. Meanwhile, in Berlin, Mrs Merkel would be forgiven for feeling relieved. The CSU may be her CDU’s sister party but its tactics in recent months have made her job almost impossible. She will not mourn Mr Seehofer’s career if he is ousted in the coming days. Moreover, the CSU’s electoral meltdown will curb the enthusiasm of anti-Merkel conservatives in her own party who urged her to emulate the Söder-Seehofer playbook.

But tonight’s result also points to something broader. The CSU used to be the epitome of what Germans call “Volksparteien”, or “people’s parties”. These giant, big-tent, centre-right or centre-left forces used to have something approaching a monopoly on the politics of most Western European countries. But in most, that monopoly is disintegrating. The Gaullists and Socialists are losing their relevance in France while the far right, far left and radical centre surge. In the Netherlands, Spain, Sweden and Italy the old Christian democrats and socialists have been diminished by more vital forces on the right, left and centre. In Greece and Austria the centre-right stumbles on, but social democrats are in crisis. In Germany support for the CDU and the SPD is falling almost across the board (with a few intriguing regional exceptions), while the Greens and AfD are rising. Only in Britain are the two traditional parties still strong, but they only have their country’s profoundly distorting electoral system to thank.

The decline of the Volksparteien is fundamentally changing how Europe is run. In next year’s European election, both the European Parliament and the European Commission may become more fractious as the old duopoly of centre-right and centre-left loses its majority. At a national level, the old notion of big mainstream parties as clearing houses for differing outlooks and interests is giving way to something more tribal. Whatever you think of the CSU (and the similarly failing Bavarian SPD), recognise that their decline stands for something bigger: the end of an age of consensus and the dawn of a new age of intra-European antagonism.