Democratic Senate candidate Troy Jackson told Republican Sen. Susan Collins to "shut up" during their fourth and final debate Thursday night in Bangor, Maine, after a protester interrupted Collins, The Associated Press and Fox News reported.

The protester began shouting about data centers as Collins spoke. "I'm terrified. AI data centers are destroying our climate. They are poisoning our water," the demonstrator yelled, according to Fox News. As security led the man out, Collins said, "So, this is obviously one of Troy's supporters." Jackson shot back, "Oh, shut up," and said he did not know the protester, both outlets reported.

The Maine Republican Party called Jackson's remark "unacceptable behavior" in a social media post after the debate, and Jackson's campaign declined to comment, the AP reported.

The two also clashed over party loyalty. Asked to name a time she defied her party, Collins pointed to her effort against Pete Hegseth's nomination as defense secretary, the AP said. Jackson argued that "100% of the time when Donald Trump goes to Susan Collins for a vote, he gets it," according to the AP. Collins called herself "the most bipartisan member of the Senate," Fox News reported.

In another exchange, Jackson asked Collins whether she looked down on working-class people. "Troy, I do not look down on you or on anyone. I grew up in Caribou. My first job was picking potatoes," she replied, Fox News reported.

Collins is seeking a sixth term in a race seen as key to control of the Senate. Fox News said polls show a race within the margin of error, and leading forecasters rate it a toss-up. Jackson's campaign said it raised $20.4 million in the third quarter, while Collins' campaign reported $5.2 million, the AP said. Collins had raised more than $18 million by the end of June.

What we know: Jackson told Collins to "shut up" after she linked a protester to his campaign, and Maine Republicans criticized the remark.
What we don't: Whether the exchange will move a race that polls show is close.