The latest instance came on Monday night, where he boasted that he’s “the guy who ran against the socialists” when asked by a voter during a town hall in Miami about attacks by Republicans meant to conjure up fears about communism and socialism in Cuban and Venezuelan communities. “There’s not one syllable I’ve ever said that could lead you to believe I was a socialist or communist,” Biden said.

The comment was just one of several recent remarks that Sanders’ allies have viewed as negative in tone about progressives leading up to Nov. 3. And they come as many in Sandersworld have long resisted the urge to criticize Biden until after the election.

“It’s foolish and arrogant,” a former senior Sanders aide said in a text message to The Daily Beast late Monday night. “And more importantly, absolutely unnecessary.”

“It’s not like the Republicans are going to stop calling Biden a socialist,” the source close to Sanders continued. “This is a talking point they planned to use no matter what Democrat won the primary. Furthermore, none of his other opponents in the primary are working as hard as ‘the socialist’ to get him elected!”