Merkel’s conservative Christian Democratic Union voted with the AfD and the liberal Free Democratic Party to elect the FDP’s candidate Thomas Kemmerich as the state prime minister.

He will now replace the incumbent Bodo Ramelow from the leftist Die Linke party. Ramelow was widely expected to hold onto the role following his party’s victory in the Thuringia state elections in October.

The AfD fraction in Thuringia is known for its radicalism. It is led by Björn Höcke, an anti-immigrant former history teacher who has previously called Berlin’s Holocaust memorial a “monument of shame.” He is considered an extremist by the country’s intelligence service. An administrative court in Meiningen ruled last year that calling him a “fascist” was not a defamation, because the description was “not based on thin air but in verifiable facts.”

Outrage and protests

Merkel came out strongly against her party’s actions. Speaking during a visit to South Africa, the Chancellor called for the “unique” decision to vote with AfD to “be reversed, at least for the CDU.”

“It was a day that broke with the values of the CDU and now everything must be done to make it clear that this can in no way be brought in line with what the CDU thinks and does,” Merkel said. She said the CDU will not participate in any government formed by Kemmerich.

The vote in the regional parliament sparked protests. In Erfurt, Thuringia’s capital, crowds gathered overnight in front of the State Chancellery. A number of people built tents and brought along sleeping bags, threatening to “camp against Kemmerich” until the decision is reversed. Thousands of people were also protesting in front of the FDP headquarters in Berlin.

Some critics and political commentators compared the vote on Wednesday to the events of 1930, when the center-right parties in Thuringia were the first in Germany to form a government that included the Nazi Party.

Angela Merkel called for the

Ramelow, who was defeated by Kemmerich, posted a quote from Adolf HitIer from February 1930, in which the Nazi leader praised the party’s result in Thuringia. “We really are the decisive party today. (…) The parties in Thuringia, which previously formed the government, cannot raise a majority without our participation,” the quote read.

Kai Arzheimer, a professor of Political Science at the University of Mainz, also pointed to the history. “Most of the time, such comparisons muddy the waters, but this is uncanny,” he tweeted. He added that the AfD, and particularly its regional chapters in eastern Germany, “are pushing the limits of the ‘radical right’ moniker.”

“They are just one step away from open opposition against democracy itself,” he said.

The vote on Wednesday didn’t come out of nowhere. Centrist parties, including the CDU, suffered major losses in the Thuringia’s state elections in October, while Die Linke and AfD surged ahead.

The rise of the AfD was phenomenal. The party more than doubled its share of voters since the last state election and came in second place after Die Linke.

CNN’s Sheena McKenzie contributed to this report.