The premier of Germany's Thuringia state stepped down and called for snap elections Thursday, barely 24 hours after he was elected with the help of far-right AfD lawmakers in a vote Angela Merkel called "unforgivable".
Thomas Kemmerich, from the liberal Free Democrats (FDP), said he would apply for the regional parliament to be dissolved in response to the outrage over his appointment, which drew comparisons with the rise of the Nazis in the 1930s.
"We want new elections to remove the stain of the AfD's support from the office of the premiership," he told reporters, adding that his resignation was "unavoidable".
Kemmerich's election on Wednesday marked the first time in German post-war history that a state premier was heaved into office by accepting votes from the far right, crossing a red line in a nation haunted by its Nazi past.
He became the surprise winner of a run-off vote after AfD lawmakers ditched their own candidate to back him, in what Kemmerich called "a perfidious trick" by the far right.
Chancellor Merkel earlier called the vote "unforgivable" and said the result "must be reversed".
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She reiterated that her centre-right CDU would never work with the anti-Islam, anti-immigrant AfD, on a regional or national level.
Thousands took to the streets in cities across Germany late Wednesday to vent their dismay at the vote outcome, including in Berlin, Frankfurt and Thuringia's capital Erfurt.
Some carried signs that read "Never again" and "Voters betrayed", while others recalled that it was in Thuringia in 1930 that a Nazi minister was first allowed into government.
The aftershocks of the crisis were being felt in Berlin too, since Thuringian state lawmakers from Merkel's own CDU lined up with the FDP and far right in voting for Kemmerich over popular incumbent Bodo Ramelow from the far-left Die Linke.
Merkel's coalition partners, the centre-left Social Democratic (SPD), reacted furiously to the debacle, calling for her conservative party to clearly distance itself from the AfD if the national government is to survive.
"There can be no carrying on as usual without resolving this problem," fumed SPD co-leader Norbert Walter-Borjans.
The SPD and CDU are due to hold crisis talks in Berlin on Saturday.
Addressing the controversy during a visit to South Africa, Merkel called Wednesday's vote "a bad day for democracy" and said the role played by her local allies "broke with the values and convictions of the CDU".
"We must now do everything we can to make clear that this can in no way be reconciled with what the CDU does and thinks, and that's what we will work on in the coming days," she added.
In states across Germany's former communist east, the AfD is a major political force and mainstream parties are increasingly scrambling to keep it locked out of the corridors of power.
In Thuringia, the AfD is led by Bjoern Hoecke, one of the party's most radical figures who has called for a "180-degree turn" in Germany's atonement for Nazi crimes.
A picture of Hoecke shaking hands with Kemmerich after the election win was splashed across the front pages of several German newspapers.
"The handshake of shame", screamed best-selling daily Bild, slamming Kemmerich for "letting himself be elected by a neo-Nazi".
On social media, the picture was quickly twinned with one of Adolf Hitler shaking hands with German president Paul von Hindenburg in 1933, the year Hitler became chancellor.
Since its creation in 2003, the AfD has gone from strength to strength in Germany, capitalising on anger over Merkel's 2015 decision to allow in over a million asylum seekers.
At the last general election, the party scored almost 13 per cent nationwide and won its first seats in the German parliament.
The SPD's Walter-Borjans warned that the world was watching how Germany was dealing with the rise of the far right and the "breach in the dam" in Thuringia.
"What has happened here is a signal that we can't allow to go unanswered," he said.