While the AfD and the BSW have their differences on welfare policies, both parties share a pro-Kremlin bent in their foreign policy and reject allowing in more refugees.
On Tuesday, MPs from both parties caused a scandal when they boycotted a speech by president Vlodomir Zelensky of Ukraine in the Bundestag, Germany’s parliament.
An MP for the BSW justified the move as an act of solidarity with Ukrainians whom Mr Zelensky is “using as cannon fodder”.
German academics point to mistakes made after reunification that are fuelling populism in the east.
“There was mass unemployment in the east after reunification when industrial locations were shut down. That meant that democracy could never put its roots down,” Benjamin Höhne, a researcher at the Technical University in Chemnitz, told The Telegraph.
“Now, with massive transformations taking place in areas such as climate policies, East Germans are afraid of losing the wealth they have struggled to build up. The AfD are the only party that offers a big narrative that promises a return to the good old days,” he added.
Wages in the east have stagnated at about 80 per cent of the level of those in the west for years, while there is still not a single one of Germany’s blue chip DAX companies that has its headquarters in the east.
At the same time, billions of euros of west German tax money have been poured into rebuilding the east, with wealthier Germans still contributing to a so-called solidarity tax to pay for eastern infrastructure.
Bodo Ramelow, governor in the eastern state of Thuringia, has said that west Germans often look down on the east due to the fact that so much public money has been spent there.
“On social media I see people asking why East Germans aren’t more grateful,” Mr Ramelow said after Sunday’s vote. “But East Germans don’t need to apologise for anything … The fact that some people expect gratitude from them is worsening the problem.”
However, not everyone is convinced that the popularity of the AfD can be explained by modern events.
Party’s appeal has roots in xenophobia
British historian James Hawes has argued that the party’s appeal has its roots in a xenophobia that existed among east Germans since they colonised land east of the river Elbe that was once inhabited by Slavs starting in the 12th century.
A survey published by the University of Leipzig last year similarly concluded that a strong east Germans affinity for authoritarianism explained the party’s success.
This autumn, the rift between east and west could move closer to a permanent divide.
At elections in three east German states, the AfD are on course to emerge as winners.
In Saxony and Thuringia, where the party’s positions are so extreme that they have been put under observation by Germany’s domestic spy agency, the AfD are set to take more than 30 per cent of the vote.
With Ms Wagenkencht’s BSW also polling in double digits, a watershed moment may occur: a new state government could be formed without a single party founded in the west.