ABC News December 15, 2015

Sanders Pulls Negative Web Ad on Clinton

WATCH: ABC NEWS EXCLUSIVE: Sanders Pulls Negative Clinton Ad

Throughout his improbable run for the White House, Bernie Sanders has boasted that he “has never run a negative ad.”

That seemed to change over the weekend, when a Washington Post report noted a new digital advertisement from the Sanders campaign, portraying Hillary Clinton as a candidate funded by banks and “other big money interests.” Within hours of initial reports, the ad had been taken down.

Speaking exclusively to ABC News, Sanders insisted he has stuck to his “no attack ad” pledge – though he limited his language to television ads.

Sanders calls ad criticizing Clinton removed from his website a "gray area": "We are running a positive campaign." https://t.co/jDoCve6xEl

— ABC News Politics (@ABCPolitics) December 14, 2015

“You’re looking at someone who has never run a negative TV ad in his life and never will,” he said. “There are sometimes there are gray areas, we felt that it was a gray area, we took the ad down.”

The Vermont senator’s communications director Michael Briggs characterized the “small digital ad buy” as “a miscommunication in our communications shop,” and disputed the idea that it was a full-blown attack ad.

“We make comparisons,” he said of his team’s strategy regarding Hillary Clinton.

Sanders has made the source of donations a frequent point of comparison over the last few months.

“I am the only candidate running for the Democratic nomination who does not have a Super PAC,” he boasted to New Hampshire community college students on Monday. He noted his campaign is largely bankrolled by small donors, with an average contribution of just over thirty dollars.

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The tone of the Democratic race has largely been a civil one, though Martin O’Malley has begun calling his rivals out by name leading into Saturday’s debate on ABC.

Sanders, meanwhile, said his tone on the airwaves won’t change.

“We are running a positive campaign,” he said. “Now you ask any other candidate out there if they’ve ever run negative television ads. Not one of them will say they haven’t. I have not.”

His campaign denied there any other negative ads waiting in the wings should the nature of the race change.