Sen. Susan Collins, R-Maine, fired back at her political opponents Thursday, telling Fox News Radio's "Guy Benson Show," that she has "never been more offended by attacks as I have been from the left in this campaign."

Collins reserved particular wrath for an ad from The Lincoln Project, a group of onetime Republican political consultants, that hit the airwaves last week and labeled her a "Trump Stooge and a "fraud" whose "voice" is controlled by President Trump and Senate Majority Leader Mitch McConnell, R-Ky.

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"The idea that I lack integrity is so false," she said. "I always do what I think is right. My vote [to confirm] Justice [Brett] Kavanaugh's an example of that."

Collins, who is seeking a fifth term against Democrat Sara Gideon, went on to describe the Lincoln Project ad as "very sexist."

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"The idea that these two men [Trump and McConnell] control my votes is absurd, and it's disproven by the facts," she said. "I've always done what I thought was right for Maine and for America regardless of who was president, and I couldn't be the one who works most across the aisle, as documented by Georgetown University ... and be anybody's stooge.

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"So it was insulting, it was untrue, and it's not worthy of the kind of races that we should be running in America, where we should have vigorous debates on votes, on differing philosophies. And that's what I've had in the past with my opponents ... but but it never degenerated into these totally false attacks that we're seeing in Maine now that are financed by the far left."