“I mean he’s totally unhinged,” she said.
She also accused him of being behind an R.N.C. member’s plan to use a resolution to try to force the party to say the nominating contest was effectively over. But the plan was withdrawn after Mr. Trump rejected it in a post on his Truth Social website.
Ms. Haley, who lost to Mr. Trump, the G.O.P. front-runner, by about 11 percentage points on Tuesday in the New Hampshire primary, has vowed that she will continue her uphill campaign.
Mr. Trump’s campaign spokesman, Steven Cheung, used Mr. Trump’s derogatory nickname for Ms. Haley, “birdbrain” and said she “is trying to grasp at straws to gaslight voters because she’s nothing more than a Democrat with America Last policies that will destroy the country.”
The tenor between Ms. Haley and Mr. Trump has grown increasingly caustic since the race narrowed to just the two of them. Ms. Haley first hit at his age in the days ahead of the New Hampshire primary, suggesting that “there is a decline.” Mr. Trump seethed at her refusal to quit the race in his victory speech.
In the Fox interview, she pushed back against the narrative that her loss in New Hampshire — where it was a two-candidate race — and her third-place finish in the Iowa caucuses on Jan. 15 had left her an extremely narrow pathway to the nomination. Mr. Trump holds a commanding polling lead in South Carolina, her home state and the next major contest between them.