(Bloomberg Opinion) — It’s long been obvious that one of Germany’s formerly grand centrist parties, the left-leaning SPD, is in decline. But another and even grander centrist bloc, the Christian Democratic Union of Chancellor Angela Merkel, had hopes of avoiding that fate, by defending the hallowed middle ground in politics. Suddenly, though, Germany is having a full-bore political crisis of centrism.Since Feb. 10, when the CDU’s chairwoman, Annegret Kramp-Karrenbauer, shocked the country by announcing that she would stand down, the party has descended into a leadership vacuum and an uncharacteristic bout of internal chaos. It now plans to clarify its succession at a party conference on April 25. Until then, the position as the CDU’s next boss and the party’s future direction are both up for grabs. So is German, and even European, politics, because the party’s new leader is also likely to be its candidate to succeed Merkel as chancellor.Germans are already punishing the CDU for the turmoil. On Feb. 23 only about 11% of voters in Hamburg plumped for the party, its lowest share in that city state since World War II. That follows setbacks in other big cities. Though still the strongest bloc nationally, the CDU is gradually becoming a redoubt of the rural and the old.More dramatically, the Christian Democrats in the eastern state of Thuringia are rebelling against their party’s national leaders, as they contemplate whether and how to collaborate with the post-communist Left Party, which the CDU officially considers a pariah. That follows the Thuringian CDU’s disastrous decision on Feb. 5  — also in defiance of party bosses — to cooperate tacitly with the extreme-right Alternative for Germany (AfD), triggering a constitutional crisis in the state.Are the CDU’s travails in Thuringia a harbinger of things to come in national politics, and perhaps in Europe as a whole? The ruckus may be another warning that centrism as such is losing its viability or even meaning.The CDU and its Bavarian sister party, the CSU, were born in the immediate post-war years as “Christian unions” in the sense that they mopped up former parties of the Weimar era that appealed narrowly either to Catholics or Protestants. That early preponderance of clergy gave the bloc its color in the spectrum of German parties: black, like the robes.From the start, the Union, as the pair are jointly known, amalgamated a range of interest groups, from cultural conservatives to Catholic quasi-socialists and free-market liberals. Unlike the “red” SPD, which appealed to blue-collar workers, “black” was always a big tent. Its pitch was never ideological purity but tight discipline among the rank and file and pragmatism in government. Tellingly, its winning slogan in 1957 was “no experiments.” Pundits dubbed it a “club for the election of chancellors” — the CDU has fielded five of post-war Germany’s eight leaders.One of the Union’s roles was to be a bulwark against extremism. Franz Josef Strauss, a grandee of the CSU, famously said that there must never be a legitimate party to the Union’s right. Nowadays, of course, there is, after the AfD entered the federal parliament in 2017. One theory is that Merkel bears part of the responsibility for its rise. As CDU leader from 2000 to 2018 and chancellor since 2005, she tried to modernize her party by nudging it further left, thus alienating conservatives and leaving the right flank open.The stated policy of the CDU and CSU has always been to shun and shame the AfD. According to a so-called “horseshoe theory” that regards far left and far right as equally dangerous, the Union also spurns the Left, which descends from the Communist Party of the former East Germany, contains radical factions, disdains NATO and coddles Russia.The problems with horseshoe shaming have become clear in Thuringia. The state is unusual in that the centrist parties are already in a minority in the local legislature, and the AfD and Left together have the majority. By simple arithmetic, as long as all centrist parties rule out any cooperation, even of the passive sort, with both the far left and right, there will be stalemate. Who can and will govern Thuringia remains unclear.Another question is whether the symmetrical treatment of far left and right still makes political sense. After a racist murder rampage by a right-winger, some of the AfD’s political rhetoric increasingly sounds like demagogic arson. By contrast, the Left may be unsavory, but in eastern Germany it’s part of the woodwork. Its Thuringian candidate, Bodo Ramelow, is pragmatic and harmless, almost bourgeois.Nonetheless, the candidates now jostling to lead the CDU fear touching anybody on left or right. “If we start voting for Mr. Ramelow as premier, then we can’t represent the center anymore,” says Norbert Roettgen, one of the runners to replace Kramp-Karrenbauer.The sentiment is understandable. And yet, German and European politics keeps fragmenting. Sooner or later this will necessitate new, strange, even awkward forms of parliamentary collaboration — not to betray but to save democracy. Otherwise centrists may find that treading the middle of an ever busier road will get them run over.(This column was updated to correct the date of the CDU conference in April.)To contact the author of this story: Andreas Kluth at akluth1@bloomberg.netTo contact the editor responsible for this story: James Boxell at jboxell@bloomberg.netThis column does not necessarily reflect the opinion of Bloomberg LP and its owners.Andreas Kluth is a member of Bloomberg’s editorial board. He was previously editor in chief of Handelsblatt Global and a writer for the Economist. For more articles like this, please visit us at bloomberg.com/opinionSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.