Nadir Aslam, a German of Moroccan-Pakistani heritage, had been planning to vote Green in this week's elections to the European Parliament. Instead, he will throw his support behind Mera25, a startup leftist party with a clear pro-Palestinian stance.

Aslam, 33, said it was a speech last November by a Green leader doubling down on German support for Israel, even as the Gaza death toll neared 9,000, which "destroyed" his support for the ecologist party, a member of Germany's ruling coalition.

This shift in support, echoed across Europe, represents the latest threat — this time from the left — to mainstream political parties whose project to deepen European integration is already under attack from the far-right. The trend is not only among the EU's Muslim communities but also among left-leaning voters who see a double standard in Europe's condemnation of the Oct. 7 Hamas attack on Israel but failure to call out Israel for its military assault on Gaza which has killed more than 36,000 Palestinians.