Bernie Sanders’ presidential campaign has begun raising money for Democratic National Committee chair Rep. Debbie Wasserman Schultz’s primary opponent, threatening to further divide Democrats even as Party leaders hope to unite the Party behind Hillary Clinton.

Sanders spoke out against Wasserman Schultz in an interview that aired Sunday on CNN, during which he said he “clearly” favored her opponent, Tim Canova. Now, he’s wading in with an active role against her.