Angela Merkel has often been prematurely written off in the past. But the aftermath of the regional election in Hesse has proved the beginning of the end for 21st-century Germany’s – and Europe’s – dominant politician. Mrs Merkel’s centre-right CDU hung on as the leading party in Hesse, which is dominated by the country’s financial capital, Frankfurt. But this was its worst showing in this heartland region in half a century and the latest in a string of poor election performances. Mrs Merkel bowed to what has become increasingly inevitable since the inconclusive general election of 2017, and announced she is stepping down as CDU chair and will retire as chancellor in 2021.

Leaders who pre-announce their retirement always struggle not to become lame ducks. Mrs Merkel’s twilight period clearly now runs that risk, with major consequences for Germany and Europe. She remains popular in Germany, however, and she may possess the skills and authority to defy convention and last another three years. However, December’s election of a new CDU chair will be widely seen as producing a CDU chancellor-candidate in waiting who will want to make a mark of their own. Mrs Merkel’s federal coalition partner, the social democratic SPD, is in an even worse electoral eclipse than the CDU right now, but it may nevertheless come under grassroots pressure to force fresh elections.

The Hesse result follows a similar pattern to the one in Bavaria two weeks earlier and the federal election of September last year, with centre parties losing votes to radical alternatives of all kinds. On Sunday one in five of Hesse’s voters deserted the CDU and the SPD. The CDU’s result was its worst in Hesse since 1966; the SPD’s its worst there since 1946. The corollary of the weakened centre was a Green surge on the left – the Greens have been the CDU’s junior coalition partner in Hesse since 2013 – and an anti-immigrant AFD surge on the right, while the smaller liberal FDP and the leftwing Linke party both posted modest gains too. The upshot is further fragmentation of Germany’s old two-party system.

The crisis for the SPD is arguably more profound than the one that faces the CDU. Having failed to mount an effective defence of key parts of Germany’s postwar social settlement in the 1990s, and lacking a political narrative that speaks to and for a new generation of precarious low-wage workers in an era of global labour mobility, the SPD is unsurprisingly continuing to suffer for its role as Mrs Merkel’s grudging coalition partner. As a result, Europe’s historically most important centre-left party is now looking into the same oblivion into which once mighty sister parties in France, Greece and the Netherlands have already fallen. Grassroots pressure to emulate Labour’s turn to the left in Britain is certain to grow. The politics of Germany, so stable for so long, are now full of uncertainties that will resonate far beyond Berlin.

Mrs Merkel has dominated politics in Germany for so long that her departure is bound to be traumatic. She has stood consistently for the German social market model at a time when its twin pillars, social justice and sound finance, have each come under challenge. Her country’s economic strength has protected many Germans from the stresses that other nations have suffered. But the migration crisis of 2015 – on which she took a liberal, pragmatic line – has had consequences that she has been unable to master. Mrs Merkel’s successor will have to learn from her strengths as well as her failings in the vital task of rebuilding confidence across our anxious continent.