The far-right Alternative für Deutschland has won a district council election in Germany for the first time, in what is being referred to as a watershed moment in the country’s politics. The eastern town of Sonneberg, in the state of Thuringia, elected Robert Sesselmann to the post of district administrator, the equivalent of a mayor, with 52.8% of the vote, ousting the Christian Democrats’ (CDU) Jurgen Köpper on 47.2%. The Thuringia branch of the anti-immigrant party has been classed as rightwing extremist by intelligence services. It is led by Björn Höcke, who is considered to be part of the AfD’s far right or völkisch wing, which was officially disbanded but is still widely believed to exist. Observers say the win, which AfD’s leadership said would give the party a much-needed boost in its efforts to expand its influence across Germany, could be a bellwether for upcoming votes, in particular in the east. State parliament elections are taking place next year in Saxony, Thuringia and Brandenburg. Established parties from the Social Democrats to the CDU as well as civil society organisations called the result a turning point to which defenders of democracy would be forced to find a way of responding. The Central Council of Jews in Germany said it was devastated by the result. “To be clear, not everyone who voted for the AfD has a rightwing extremist mindset,” its president, Josef Schuster, told the Jüdische Allgemeine newspaper. “But the party whose candidate they have elected is, according to the regional intelligence service, rightwing extremist … This is the bursting of a dam, which the political powers in this country cannot simply take on the chin.” Christoph Heubner, the executive vice-president of the International Auschwitz Committee, called it a “sad day” for Sonneberg, Germany and democracy. “A majority of voters have turned their backs on democracy and deliberately decided in favour of a rightwing extremist, Nazi-dominated party of destruction,” he said. Sonneberg, which has about 57,000 inhabitants, is one of Germany’s smallest administrative regions, and voter participation was low at just 58%. However, the result’s significance goes far beyond the town itself, and this was being recognised across the country on Monday. Political scientists called it a warning to the established parties, which had joined forces and, along with other organisations such as trade unions, urged voters to abandon any existing party loyalties and back Köpper in an effort to squeeze Sesselmann out of the running, a move that appears to have backfired. The AfD’s procurement of the most important political office in Sonneberg coincides with some of its strongest nationwide polling results recently, of between 18 and 20%. Its rise in support has been at least in part put down to disgruntlement over infighting within the centre-left federal coalition government led by the Social Democrats, with the Greens and the pro-business Free Democratic party, as it tackles big restructuring projects in key areas, from energy procurement to military strength, migration policy to health reform. Latest polls showed the AfD on 20%, more than double what its support was a year ago, and similar to the Social Democrats, with the Greens on 13% and the opposition CDU on 26%. The AfD was founded in 2013 by a group of Eurosceptic academics and bankers. It later campaigned on an anti-immigration ticket, entering the national parliament for the first time in 2017. Its focus became what it called the over-Islamification of Germany, before, more recently, it turned its attention towards the government’s building energy law that is making its way through parliament, comparing the attempts to outlaw the installation of new gas heaters to the strictures of a dictatorship. It has also been critical of the government’s support for Ukraine. As part of his campaign, Sesselmann called for the government of Olaf Scholz to strive for a peace agreement with Moscow over its invasion of Ukraine, and opposed Germany’s military support to Kyiv. While locals voiced concerns on these issues, they more often cited dissatisfaction over living standards and low pay and pensions compared with their western German counterparts, as well as a feeling that their backgrounds, as citizens of the former communist east, were not taken seriously. Bodo Ramelow, the state leader of Thuringia from the far-left Die Linke, called Sonneberg’s election result “a signal of dissatisfaction”. He called for a debate to “redefine the spirit of German unity, in which we take east Germans with us rather than triggering the feeling that they are being laughed at or merely being talked about”. Tino Chrupalla, a co-leader of the AfD, tweeted: “That was just the beginning. We will convince the majority with our politics of showing an interest in the people. This is how we will turn the tide for the better.”