WASHINGTON (AP) — Maine Democrat Troy Jackson says he does not regret telling Sen. Susan Collins that she should “shut up” after the Republican suggested a protester who interrupted their recent debate was one of his campaign’s backers.

“She said that it was a Troy supporter. She accused me of setting that up. I had no idea who it was,” said Jackson, a former president of the state Senate who is trying to deny Collins, the longest-serving Republican woman in Senate history, a sixth-term. He spoke in an interview with CNN’s “State of the Union” that aired Sunday.

During their final debate Thursday night in the closely contested race, as the Nov. 3 election nears a protester opposing data centers began yelling as Collins spoke. While moderators asked for that person to be removed, the senator said the demonstrator was “obviously one of Troy’s supporters.”

Jackson responded: “Oh, shut up. I don’t even know that kid.”

The Sunrise Movement group posted on its Instagram page that the outburst came from one of its members. In a caption of an Instagram post, the group’s page said: “We’re proud of this Sunrise volunteer who took action yesterday.”

The New York Times said the protester, Henry Elgie, a 19-year-old student at Bowdoin College in Maine, told the newspaper in an interview Saturday that he had “zero coordination” with Jackson’s campaign. “I do not know Troy Jackson personally or at all,” he was quoted as saying.

The Sunrise Movement is a left-wing political advocacy organization that champions the Green New Deal, aimed at transitioning the U.S. economy to 100% renewable energy. The group, which has local arms around the country, regularly organizes protests, sit-ins and climate strikes.

Jackson told CNN that he shook hands with Collins after each of their debates.

“But what I’m not going to be is talked down to by Sen. Collins,” he said. He added: “I’m fighting for Mainers and I just think that was another situation where she was talking down to me and I’m not going to apologize for that.”

Collins told Fox News’ Sean Hannity on Friday that she was “struck by how reflective the response, ‘Oh, shut up,’ was.” Collins said “the fact that it seemed like such an automatic, quick reply was very telling.”

She cited what she said was “the reputation” that Jackson had in the Legislature “particularly when he’s dealing with women with whom he disagrees. So in some ways it didn’t surprise me.”

Some state lawmakers who worked with Jackson have criticized him as having a temper, including once throwing a plastic water bottle on the ground in frustration while disagreeing with a female lawmaker. Asked by reporters during the campaign about the confrontations, Jackson said, “I wear my heart on my sleeve.” He took responsibility for his outburst and apologized to those he had confrontations with at the time.

Jackson was asked on CNN about some Republicans who are saying there were stories that he was aggressive in his tone to women from his time in the Legislature and that his remark Thursday night was another example of that.

Jackson said some Republicans have been spending millions “attacking me and my family, making untrue claims. … So it doesn’t surprise me.”