Vermont Sen. Bernie Sanders on Tuesday night sought to fully divorce himself from supporters who have harassed others online and questioned whether anyone who believes in his agenda would attack a union leader.
Top officials at the Culinary Union in Nevada accused Sanders supporters of swarming them online after the union distributed fliers that said Sanders would "end" their health care.
Sanders at a CNN town hall questioned whether some of the social media comments cited by critics were, in fact, written by his supporters.
"The idea that anybody who works with me would make a vicious attack against a union leader just because we disagree on an issue is incomprehensible to me," Sanders said. "And you know what, I'm just not sure that that's true."
He also pointed out that members of his own staff had been the targets of online harassment.
"Talk to the people in my campaign, often the African American women in this campaign, talk to my wife, about the kind of ugly attacks that have come in to us," he said.
On the broader issue, Sanders was -- in his final point on the question -- unequivocal.
"I do not believe in online bullying," he said. "End of discussion."
Sanders also had a message for his supporters.
"Anybody out there who claims to be a Bernie Sanders supporter: we work with the unions. This is a union-led campaign. We believe in unions. We will never attack union leadership and we will not attack people on a personal basis," he said.
Culinary Union spokeswoman Bethany Khan told CNN the organization took hits last week on Twitter for the "Medicare for All" position, with some staffers receiving direct messages. Khan also said some critics have called the union's phone lines and left messages attacking them for opposing the health care plan.
The flier distributed by the Culinary Union outlines where the leading 2020 Democratic candidates stand on health care, immigration and jobs. It singles out Sanders as the candidate who will end the union's health care among the top six Democratic candidates, pointing to his Medicare for All plan.
The release of the flier by the union, which is a force in Nevada politics, came just a week and a half away from the Nevada caucuses.
The organization, which declined to endorse a 2020 candidate, says it represents 60,000 hotel and casino workers in Nevada and provides health insurance coverage for more than 130,000 people. Its organizing abilities have helped deliver the state for Democrats for years.