The campaign of the senator from Vermont has told some supporters picked to represent him this year to sign agreements barring attacks on other candidates or party leaders, combative confrontations on social media or talking to reporters without approval.

The move, which carried a threat of being removed as a delegate, has the effect of blunting one of the most powerful if divisive tools of Sanders’s movement — its unrestrained online presence and tendency to stoke controversy through other media, which has at times spiraled into abuse of his opponents, perceived and real.

“Refrain from making negative statements about other candidates, party leaders, Campaigns, Campaign staffers, supporters, news organizations or journalists. This Campaign is about the issues and finding solutions to America’s problems,” said the social media policy sent to some delegates. “Our job is to differentiate the senator from his opponents on the issues — not through personal attacks.”

“Do your best to avoid online arguments or confrontations,” the policy said. “If engaging in an adversarial conversation, be respectful when addressing opposing viewpoints or commenting on the opposition.”