Attorney General of Minnesota Keith Ellison asked on Thursday whether anyone could send him an "example" of a Bernie Sanders supporter being bad," noting that he's "never seen" one of Sanders' fans be "unusally mean or rude."

Rep. Steve Scalise, R-La., who was shot and nearly killed at a congressional baseball practice by a Bernie Sanders supporter in 2017, responded flatly, "I can think of an example."

The moment highlighted a brewing internal fight among Democrats after Wednesday night's contentious presidential primary debate: Are candidates responsible for the conduct of their supporters in an increasingly heated election year?

Ellison, in his tweet, asked the same question, seemingly suggesting that the standard would be impossible for candidates to meet. But, top contenders for the Democratic nomination have argued otherwise.

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"Look, I have said many times before -- we are all responsible for our supporters," Warren told moderator Hallie Jackson at the NBC/MSNBC debate. "And, we need to step up. That's what leadership is all about. But the way we are going to lead this country and beat Donald Trump is going to be with a candidate who has rock solid values and who actually gets something done."

Her response came in response to Jackson's question referencing Joe Biden's comments on Sunday accusing Sanders supporters of bullying union leaders with "vicious, malicious, misogynistic things." Biden, speaking on NBC's "Meet the Press," had called on Sanders to disavow online activists spreading hate in his name.

"I know you've seen what's been online," Biden said. "The vicious, vicious threats and things they've said, the misogynistic things they've said, referring to the women who are leaders of the Culinary Union and the things that they've said about them. And, actually, they've received death threats. I mean, this is way, way -- this is Trump-like -- way over the line. And I think Bernie has to be -- he has to disavow this. He has to say, 'I disassociate, I don't want any of those people being with me.'"

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And, Mike Bloomberg, in a tweet earlier this week, highlighted political posts by online antagonists with the caption: "We need to unite to defeat Trump in November. This type of 'energy' is not going to get us there."

President Trump, during his post-impeachment trial press conference earlier this month, recounted the Scalise shooting at length -- in a possible sign that he won't be afraid to bring up the issue should Democrats try to hold Trump responsible for supporters' conduct later this year.

"He got whacked,” Trump said, referring to Scalise. “He got whacked. My Steve, right? I went to the hospital with our great first lady that night — right, honey? — and we saw a man that was not going to make it.”

The Sanders supporter, James Hodgkinson, also used his rifle to shoot U.S. Capitol Police officer Crystal Griner, congressional staffer Zack Barth and lobbyist Matt Mika, before police and Scalia's security detail shot and killed him. Trump praised officers for responding bravely even though they only had handguns.

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Trump added: “A lot of wives wouldn’t give a damn. A lot of wives would’ve said, how is he doing? She couldn’t even talk, she was inconsolable,” Trump said. “Most wives would say, not good, listen I’m going home now. The doctor came in and the wife was a total mess. She was really devastated. It really looked like he had a 20, 25 percent chance.”

At the time, Trump said, Scalise wasn't "that good-looking. You look good now. ... He looks better now, can you believe it? I don’t know what the hell that is. It’s true. Better now.”