Sen. Susan Collins (R-ME) was completely unruffled Wednesday by the prospect of a challenge from Obama’s former ambassador to the United Nations Susan Rice.

"I really have little interest in what she has to say," Collins told CNN Wednesday, adding, "she's not a legal resident of the state of Maine."

Collins coolly pointed out that if Rice wanted to run against her in 2020, "she'd have to move to the state to become a legal resident."

As many Democrats slammed Sen. Collins’s vote to confirm Kavanauagh, Rice signaled on Twitter that she would run against the moderate Republican in 2020.

"I have been moved by the enthusiasm," Rice later told The New Yorker. "I’m going to give it due consideration after the midterms."

Rice also defended her “ties” to Maine during the New Yorker event.

"My ties to Maine are long and deep," she argued. "My family goes back generations. My grandparents emigrated to Portland, Maine, in 1912. They stayed in Maine until they died; they raised five children there. For the last twenty years, I’ve been a homeowner in the state of Maine."

Collins challenged those ties Sunday on CNN’s “State of the Union.”

"As far as Susan Rice is concerned, her family has a home in Maine, but she doesn't live in the state of Maine,” she said. “Everybody knows that."

Sen. Susan Collins was a key vote in Kavanaugh’s confirmation process and has faced ugly threats over her decision. Leftist groups in Maine have pledged over $3 million to Collins's 2020 opponent due to her vote on Kavanaugh.

In a speech last Friday justifying her vote, Collins concluded that since Dr. Christine Blasey Ford, the woman accusing Kavanaugh of sexual misconduct, had named four witnesses who could not corroborate her account she did not think Ford's claims met a "more likely than not" standard. She also defended Kavanaugh's judicial record and temperament.