A series of potential scandals is plaguing the far-right Alternative for Germany party ahead of next month's European Parliament elections.

The party has struggled to explain a number of murky donations to prominent party members in recent months. German authorities are investigating who the money came from.

In addition, German broadcaster ZDF reported Friday that Russian officials in 2017 described one of the party's lawmakers, Markus Frohnmaier, as "absolutely under our control." Frohnmaier denies the claim.

A poll published Sunday by German weekly Bild am Sonntag found the party's support has fallen to 12% — its lowest value in year. The survey of 2,355 respondents between March 28 and April 3 asked about national elections, but recent polls for the May 23-26 European vote have reflected similar or lower support.