The populist far-right, anti-immigration Alternative für Deutschland has emerged as the winner in a crucial state election in Germany, exit polls have projected, securing a historic result and more than doubling its support, and appearing to be on the brink of becoming the first far-right party to gain power at state level since the second world war.

Initial exit polls showed the party to have secured 44.4% of the vote, ahead of predictions and decisively ahead of the Christian Democrats (CDU) of the chancellor, Friedrich Merz, in a contest that was being followed across the world. However, it still remains unclear as to how and whether it will be able to form a government, having ruled out entering a coalition, and being refused any form of cooperation by the mainstream parties.

The CDU was trailing massively on around 18.4% and the far-left Die Linke was third with 9.3%, with the Social Democrats on 8.4% and the Greens on 8.7% by around early evening. The smaller BSW reached the 5% hurdle needed to re-enter parliament, against expectations.

Participation was at a record high of 76.5%.

Votes are still being counted, but it appeared initially that the AfD might have failed to secure an absolute majority, the condition it has said is central to it taking power, over its refusal to govern with another party.

The CDU and all other mainstream parties have also refused to collude with the AfD in a government, in what is referred to as a Brandmauer, or firewall. The AfD in Saxony-Anhalt has been classed as “rightwing extremist” by Germany’s domestic intelligence agency.

Addressing jubilant supporters, Ulrich Siegmund, the AfD’s lead candidate in Saxony-Anhalt, said: “We have made history in this country”. Speaking to public broadcaster ARD, he said his party was ready to ⁠reach out ​to ‌all powers ‌that ‌strove for political change.

“We extend a hand to all ‌democratic forces that wish to pursue ​better policies,” a beaming Siegmund said after ⁠exit polls had been published. He said themes such as migration and domestic security were not up for debate.

The CDU described its result as “bitter” but said it would not back down from its refusal to rule together with the AfD, which the far-right party has also ruled out.

Franziska Hoppermann, general secretary of the CDU, called it a “defeat overall” for the Christian Democrats. “And it is also a defeat for all those who have borne responsibility in the democracy in Saxony-Anhalt over the past 35 years,” she added, in reference to the difficult post-communist era.

She ruled out any discussion over Merz’s future, which analysts have suggested will make this increasingly a topic of debate after his party’s defeat. Only 9% of voters in Saxony-Anhalt in one recent poll said they were satisfied with Merz’s politics. Siegmund on Sunday evening called Merz “a very good campaigner for the AfD.”

Alice Weidel, the AfD’s co-leader, said the result gave her party a “clear government mandate” and it would “talk to all the parties” to work out a strategy as to how the AfD could rule.

About 1.7 million people were eligible to vote in the east-central state of 2.1 million residents.

Final polls had shown the AfD to have around 40-41% of support and the party appears to have almost doubled its 2021 result of 23.7%.

The number of undecided voters in advance of the vote was much lower than at previous elections, polling showed.

The small state has been governed since 2002 by Merz’s conservative CDU, together with two smaller parties.

The Saxony-Anhalt election had been seen as the biggest test yet for Merz, who is very unpopular, along with his government – a coalition with the SPD – having failed in his promises so far to reset Germany’s struggling economy or stop the rise of the AfD, which has been making regular and steady gains since it entered parliament in 2017 and is now the Bundestag’s leading opposition party. Irregular immigration has reduced since Merz has been in office, but not to the extent that it has appeased the average voter.

In national polls, the CDU has also been overtaken by the AfD, which has it eyes on victory at the next federal elections in 2029 or 2033.

If the AfD manages to form a government in Saxony-Anhalt, Siegmund has promised to immediately start a remigration and deportation offensive, ban rainbow flags in schools, and halt the building of new windfarms.

He wants to change the slogan of the state from “Think Modern” to “Think German”, and to reintroduce the singing of the German national anthem in schools.

Siegmund also sought in the campaign to capitalise on a mood of “ostalgie” or nostalgia for communist East Germany, and to tap into discontent among east Germans. He has made repeated references to a rise in foreigner-related crime, even as the crime rate has fallen dramatically.

Siegmund turned up to vote on Sunday morning with his wife, riding an East German-era moped in the party colours, which was also a prominent prop during the election campaign in rallies across the state. In a statement in front of the polling station, he voiced his optimism that the party would achieve “45%, and some”, and saying he wanted to “build bridges”.

Tensions before the election were high, with a considerable police presence and a number of demonstrations taking place across the state. Thousands of opponents of the AfD gathered in the state capital, Magdeburg, on Saturday, for a “festival of democracy”.

On Saturday evening, a message beamed on to the facade of Magdeburg Cathedral read: “We do not abandon what we love. True love of the homeland is not the AfD.”

The bishop of Magdeburg, Gerhard Feige, in an address to a gathering of churchgoers, warned against forces “that want to sow discord, stoke mistrust and fear”. He drew parallels with history, warning that a democracy has the potential to abolish itself. “Not everyone who votes or is elected democratically is a democrat,” he said.

The German Economic Institute has warned of the far-reaching consequences for the German economy, in Saxony-Anhalt and beyond. It said the AfD’s immigration policy would be “calamitous” for the state, which has an ageing, dwindling population and is heavily dependent on foreign workers.

Critics have also warned that an AfD-run state, due to the Kremlin-friendly stance of the party, could leak sensitive information to Russia. The AfD has dismissed such claims. It has said it would seek to reform the domestic intelligence service, calling it biased.