Sanders, a progressive who bills himself as a champion of organized labor, did not acknowledge his own supporters’ alleged abusive behavior specifically and applied his call for an end to harassment to all campaigns’ backers, but said members of his movement must be “respectful.”

“Harassment of all forms is unacceptable to me, and we urge supporters of all campaigns not to engage in bullying or ugly personal attacks,” he said in a statement.

In an interview on “PBS NewsHour” on Thursday, Sanders added: “Anybody making personal attacks against anybody else in my name is not part of our movement. We don’t want them. And I’m not so sure, to be honest with you, that they are necessarily part of our movement.”