Is an increasingly nasty Clinton-Sanders race doing lasting damage to Democrats?

“There are policy disagreements he may have with her on some things — let’s stick to those, let’s not say that the most qualified candidate for president is simply unqualified,” said Sen. Claire McCaskill (D-Mo.). “We’ve got to refrain from ad hominem attacks . . . we’ve got to stay focused on what we’ve got to do in November.”

“It concerns me deeply,” said Sen. Dianne Feinstein (D-Calif.). “What he does is divide the Democratic faithful, and why would he want to do that?”

Some Democrats said they found Sanders’s words particularly troubling because, outside the heat of the campaign trail, they don’t really think he means them.

“I really don’t think he believes that,” said Sen. Timothy M. Kaine (D-Va.), another Clinton supporter. “Nothing he’s ever said to us had conveyed that sentiment. Competition’s tough. I hope that they might back off it a little bit.”