The nationalist Alternative for Germany party has been battered by a series of scandals since its founding four years ago.
Here are five controversies that have affected the party's image in recent months:
- Why populists and rightists have been in power for such a long time
- Are Putin and Wikileaks working for Trump?
- Merkel to Erdogan: Nazi comparisons must stop
Senior party member Bjoern Hoecke suggested it was time for Germans to make a "180-degree turn" when it comes to commemorating the country's wartime past.
Hoecke, a high school history teacher, said in January that Germany needs to embrace a "confident patriotism" and said no other nation would put a "memorial of shame" in the heart of its capital.
He was referring to the Holocaust memorial in Berlin, which commemorates the murder of some 6 million Jews by Nazi Germany.
The speech was widely condemned and he was reprimanded by the party. Frauke Petry, one of the party's co-leaders, has called for his expulsion.
A trip to Moscow by Petry, considered the public face of AfD, prompted concern about her party's ties to Russian President Vladimir Putin.
The trip in February hadn't been announced and AfD issued a terse statement only after the Russian parliament posted word of the meeting on its website.
The German government has warned that Russia might try to influence the upcoming general election.
Petry's office declined to answer questions about the trip, but insisted that the presence of Vladimir Zhirinovsky - a Russian far-right lawmaker once banned from Germany over his extremist views - wasn't planned.
The event wasn't welcomed by everyone in AfD. Some senior members consider Le Pen's National Front to be a socialist party whose protectionist economic policies are antithetical to those of AfD.
Leaflets promoting the party appeared in letterboxes ahead of elections in three German states last year. AfD denied that it was involved in the advertising campaign, which experts said probably cost a high six-figure sum.
Parliament investigated whether the leaflets constituted an illicit form of party funding, but concluded that no wrongdoing by AfD could be proven.
Revelations that an AfD lawmaker in the southwestern state of Baden-Wuerttemberg had previously written anti-Semitic texts sparked a furious row among members. The party's deputies in the state assembly briefly split into two factions before reconciling.
The lawmaker, Wolfgang Gedeon, remains a member of the party.