BERLIN — The political maneuver shaking Germany’s postwar democratic order involves a piece of legislation that is about as mundane as it gets.

Center-right legislators in the eastern German state of Thuringia wanted to cut a local property tax by a small amount — and did so with the support of the far-right Alternative for Germany, or AfD.

The move broke with years of tradition in which mainstream parties have vowed to maintain a Brandmauer, or firewall, between themselves and the AfD, a party many in a country alert to the legacy of Nazism see as a dire threat to democracy. Even accepting the party’s support, the thinking goes, would legitimize far-right forces or make them salonfähig — socially acceptable.

And so, when parliamentarians from the conservative Christian Democratic Union, or CDU, passed the tax reduction on a late afternoon in September with AfD votes, it sent tremors across the country’s political landscape that still are reverberating.

“For me, a taboo has been broken,” Katrin Göring-Eckardt, a leader of the Greens who hails from Thuringia, said after the vote. “It shows me not only that the firewall is gone, but that there is open collaboration.”

For mainstream parties, and the CDU in particular, the question of how to handle the growing presence of far-right radicals in governing bodies from federal and state parliaments to local councils is likely to grow only more vexing.

That especially is the case in the states of the former East Germany, where the AfD now leads in polls at around 28 percent. Next year, the eastern states of Thuringia, Saxony and Brandenburg will all hold parliamentary elections. Polls show the party leading in all three states.

The AfD is likely to expand its presence in the parliaments of Bavaria and Hesse when those states vote on Sunday. In Hesse, the AfD is coming close to overtaking German Chancellor Olaf Scholz’s center-left Social Democratic Party, according to the latest polls.

The dilemma facing mainstream parties is clear. To work with the AfD means to normalize a party that many believe seeks to subvert the republic from within. But to ostracize the party only alienates its many voters.

The firewall also serves as an unintended political gift, allowing the AfD to depict itself — at a time of high dissatisfaction with mainstream parties — as the clear choice for those who want to send a burn-it-down message to the country’s political establishment.

At the same time, the controversy over the latest vote in Thuringia seems to have played into the AfD’s hands, allowing the party to depict itself as seeking to uphold rather than undermine democracy.

The “‘firewall’ is history — and Thuringia is just the beginning,” AfD party leader Alice Weidel posted on X, formerly Twitter, after the vote. “It’s time to respond to the democratic will of citizens everywhere in Germany.”

Historic fears

Germany’s political leaders are all too aware that the Nazi seizure of power began with democratic electoral success. In fact, it was in Thuringia where, in 1930, the Nazi party first took real governing power in coalition with conservative parties.

That fact was not lost on the CDU’s opponents.

“German conservatism has already been a stirrup holder of fascism,” Janine Wissler, a head of the Left party, told the German Press Agency after the vote. “Back then, too, it started in Thuringia,” she added. “Instead of having learned from that, the CDU is going down a path that’s as dangerous as fire.”

CDU leaders in Thuringia deny the vote on the tax reduction means the firewall is crumbling. They say there was no cooperation with the AfD ahead of the vote (though AfD members say there were discussions between lawmakers).

“I cannot make good, important decisions for the state that provide relief for families and the economy dependent on the fact that the wrong people might agree,” Mario Voigt, the head of the CDU in Thuringia said after the vote.

Friedrich Merz, the national leader of the CDU, has sent mixed signals on the firewall — or at least on what exactly the firewall means. Merz says the CDU will not form coalitions with the AfD but he’s been less clear on whether the CDU will work with the party in other ways.

In a television interview over the summer, he seemed to suggest working with the AfD on the local level was all but inevitable.

“We are of course obliged to accept democratic elections,” he said. “And if a district administrator, a mayor is elected there who belongs to the AfD, it’s natural that you look for ways to then continue to work in this city.”

After an uproar ensued, Merz walked back the comment. “There will be no cooperation between the CDU and the AfD at the municipal level either,” he posted on X, formerly Twitter.

After the vote in Thuringia, Merz stood by the CDU leadership of the state. “We don’t go by who agrees, we go by what we think is right in the matter,” he said on German television.

Even some within his own party do not see things that way. Daniel Günther, the CDU premier of the northern state of Schleswig-Holstein, sharply criticized his party colleagues in Thuringia. “As a conservative, I must be able to say plainly and simply the sentence, ‘I do not form majorities with extremists,’” Günther said.

‘Cordon sanitaire’

It’s not the first time Thuringia has been at the center of a controversy over the firewall. In 2020, a little-known politician in the pro-business Free Democratic Party, Thomas Kemmerich, was elected state premier with the support of the CDU and AfD. Then-Chancellor Angela Merkel weighed in to call the vote “unforgivable.”

In the furor that followed, Kemmerich resigned as did the then-head of the CDU faction in the state. But given the AfD’s large presence in the local parliament, the issue was bound to resurface.

The problem is far from Germany’s alone. Mainstream parties are under growing pressure due to the rise of the radical right across Europe.

In France, parties from across the political spectrum have formed a cordon sanitaire, or sanitary cordon, to keep Marine Le Pen, a leader of the far-right National Rally, out of the presidency. But with Le Pen’s party now the biggest opposition group in the National Assembly, the cordon is getting harder to maintain.

In the European Parliament, where a similar cordon has been erected, the center-right European People’s Party has been openly courting the European Conservatives and Reformists, home to Poland’s nationalist Law and Justice party and Italian Prime Minister Giorgia Meloni’s far-right Brothers of Italy party.

In Thuringia, the stakes are even higher as the local branch of the AfD contains some of the party’s most extreme members. State-level intelligence authorities tasked with surveilling anti-constitutional groups have characterized the party’s local branch as extremist.

The leader of the AfD in Thuringia is Björn Höcke, who is set to face trial for using banned Nazi rhetoric. (In 2021, he closed a speech with the phrase “Alles für Deutschland!” or “Everything for Germany!” — a slogan used by Nazi stormtroopers.)

Höcke railed against Holocaust remembrance in Germany and warned of “Volkstod,” the death of the Volk, through “population replacement.” For such views, German courts have ruled that Höcke could justifiably be referred to as a fascist or Nazi.

After the vote on the property tax in Thuringia, Höcke clearly was pleased, claiming the AfD had helped enact a pragmatic policy.

“It’s simply a good day for Thuringia,” he said.

Peter Wilke contributed reporting.