Campaign officials have been pressing surrogates and other allies not to escalate combustible disputes that have recently become more personal, according to people with knowledge of the situation, including a tense fight with Joe Biden, a separate altercation with Sen. Elizabeth Warren (D-Mass.) and a renewed schism with Hillary Clinton.

Sanders issued a rare apology this week to Biden after a prominent supporter wrote an op-ed declaring that the former vice president has a “big corruption problem.” And after Clinton slammed Sanders, he sidestepped her comments instead of rebuking her.

But many Sanders supporters, and even some campaign aides, are inclined to take a more aggressive approach that they say will highlight important differences. DeMoro said that Biden has a “character issue,” and she sarcastically thanked Clinton for drawing “a lot of neutral people” to Sanders with her attacks.