A top campaign aide to Hillary Clinton said Friday that Bernie Sanders is running one of the “most negative” campaigns in history, accusing the Vermont senator of launching vicious attacks on Clinton in the run-up to the Iowa caucus.

“I think he’s running the most negative campaign of any Democratic presidential candidate,” Joel Benenson, chief strategist of Hillary for America, said Friday morning during an appearance on CNN. “I think he’s been more personal in his attacks, I think he’s been increasing it on the stump recently, and I do, I can’t think of one, even in a really hard-fought campaign in 2008, I don’t think we had the range of negativity on either side.”