A conservative German mayor’s €10,000 donation to the far-right Alternative for Germany (AfD) is making things awkward for his party’s leaders.

Bernd Prange, a Christian Democrat who serves as mayor of Altmärkische Höhe in Saxony-Anhalt, wrote in an open letter on Wednesday that he would be voting for the AfD in the state’s upcoming election on Sept. 6. “I want the AfD to become so strong in the Saxony-Anhalt election that it can govern alone,” wrote Prange.

The goal, he said, was for his own party to “finally wake up,” tear down Germany’s political firewall and abandon what he called its shift to the left.