“GRAND coalitions”, Willy Brandt apocryphally opined, “have the feel of perverse sex acts”. Such broad alliances, he thought, are unnatural and best avoided. And post-war Germans did largely avoid them: until 2005, they only had one. Since 2005, however, they have had two, and may soon have another. On Wednesday 7th February, the two main parties, the Christian Democrats (CDU) and the Social Democrats (SPD), announced a common plan for Germany’s fourth grand coalition.

The rise of fringe parties, not bonhomie, has driven the change. The FDP, or more recently the Greens, have usually been the junior partners in German coalitions. The Left Party, heirs to East Germany’s ruling communists, and now the far-right Alternative for Germany, have surged in recent elections, leaving less room for mainstream parties and fewer options for Angela Merkel and her Social Democratic counterparts.

If the grand coalition goes ahead, it will be Mrs Merkel’s third. It will also be her weakest: both the SPD and the CDU posted their worst showings since the Republic’s earliest days. Martin Schulz, the SPD’s leader, had hoped to renew the party in opposition, but instead has been coaxed back to government.

For her part, Mrs Merkel is likely to be entering the final act of her chancellorship. It seems she will end as she began, at the head of an uneasy coalition of the centre. These days, however, the centre looks smaller than ever.