Attempting to heal a rift that has turned the Democratic presidential primary unexpectedly negative this week, Sen. Bernie Sanders distanced himself Thursday from comments made by one of his own top aides.

“You know, I think that every campaign has statements come out which are inappropriate. That was inappropriate,” Sanders told MSNBC’s Thomas Roberts of a joke made by Sanders’ campaign manager recently in an interview about Democratic front-runner Hillary Clinton.

Sanders added that he has “a lot of respect for Secretary Clinton” and wants to focus on substantive differences between them. “It is not negative to be talking about differences of opinion,” he added.

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The Sanders aide, Jeff Weaver, told Bloomberg in a story that featured several other top officials that the Sanders campaign would be “willing to consider” Clinton for the role of vice president. “We’ll give her serious consideration. We’ll even interview her,” he said sarcastically.

It’s unusual for a candidate to disown comments from their own top staffers, but it comes after a week that saw unexpectedly personal clashes between two campaigns that have otherwise been marked by civility.

It started with a new line in Clinton’s stump speech that the Sanders campaign said accuses their candidate of sexism. “I’ve been told to stop shouting about gun violence,” Clinton said last Friday in Washington. “Well I’m not shouting. It’s just when women talk, people think we’re shouting.”

On Saturday night, Sanders caught the Clinton campaign off guard by using his speech at a major Democratic event in Iowa to draw his sharpest contrast yet with the former secretary of state on key progressive policy items.

Two days later, Sanders’ top strategist, Tad Devine, told reporters that his candidates’ strong words came in response to Clinton’s line about women shouting.

On Wednesday, Bloomberg published the article that included campaign manager Weaver joking about Clinton. In the same story, Devine suggested that Clinton could proverbially “get run over by a Mack truck” (presumably driven by Sanders) if she kept attacking his candidate.

Clinton campaign manager Robby Mook, who posed gamely for a photo with Weaver Saturday night before Sanders’ speech, took umbrage and saw a fundraising opportunity. “This kind of rhetoric comes as a real surprise to me, especially from a candidate who claims to be different and says he won’t go negative,” Mook said in a fundraising email to supporters Wednesday. “This campaign should be about offering forward-looking ideas to help families get ahead, not issuing threats or attacking Democrats.”

Meanwhile, Stephanie Schriock, the president of the Democratic women’s group EMiLY’s List and a top Clinton ally, took the confrontation a bit further. Schriock typically reserves her barbs for Republicans, but she said on Twitter that the Sanders team’s joke about Clinton being picked for vice president was a “condescending insult by a team who knows better.”

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Even some progressive allies of Sanders privately grumbled about the campaign’s handling of the Bloomberg story, wondering why top staffers would trash their opponent in front of a reporter, and they worried it will distract from the candidate’s message. Others suggested the mentality was a product of Sanders’ male-heavy campaign team.

Weaver defended his comments Wednesday evening to BuzzFeed on the sidelines of a Sanders event in Northern Virginia, where the candidate came out for ending the federal prohibition on marijuana.

But apparently by Thursday afternoon, when he went on MSNBC, Sanders thought the spat had become a distraction and put a foot down.