President Trump is warning potential donors to steer clear of his last primary competitor, Ambassador Nikki Haley, deriding her as a “birdbrain” on his social media platform.

Mr. Trump’s remarks followed Mrs. Haley’s vow to stay in the Republican primary despite losing to the 45th president in the Iowa caucuses and Tuesday’s New Hampshire primary.

“We were thrilled,” Mrs. Haley said about her primary performance so far at a rally before hundreds of sign-waving fans on Wednesday night at North Charleston, South Carolina. She cast her second-place New Hampshire finish as a win given how little support her campaign had in its early days.

“We got out there, and we did our thing and we said what we had to say, and then Donald Trump got out there and just threw a temper tantrum,” the former South Carolina governor added. 

That was a reference to Mr. Trump’s primary night remarks in which the former president repeatedly insulted her in a speech far angrier than his remarks after his Iowa victory.

After Mrs. Haley’s event, Mr. Trump posted to his social media platform an intimidating remark to any of his opponent’s donors.

“Anybody that makes a ‘Contribution’ to Birdbrain, from this moment forth, will be permanently barred from the MAGA camp,” Trump wrote, using the nickname he has crafted for Mrs. Haley and the abbreviation for his “Make America Great Again” slogan. “We don’t want them, and will not accept them, because we Put America First, and ALWAYS WILL!”

As he waited for Mrs. Haley at the rally Wednesday, North Charleston resident Sammy Penniger said he identified with the underdog persona that the candidate often ascribes to herself.

“She said last night, ‘I’m not going to give up,’” the 25-year-old said, referencing Mrs. Haley’s post-New Hampshire primary comments. “I kind of love that fighter mentality — that’s inspiring for a young person like me.”

Mrs. Haley, responding to Mr. Trump’s threats last night on X, offered a link to a donation platform, saying, “Well in that case…donate here. Let’s Go!” and followed by a heart emoji and an American flag. 

The threats by Mr. Trump “could complicate the decisions of some billionaires backing Haley,” the Financial Times reports, pointing to an unnamed source saying that LinkedIn co-founder Reid Hoffman, a billionaire, “has closed his wallet” to Mrs. Haley’s campaign.

Another wealthy donor, the co-founder of Home Depot, Ken Langone, has said he was waiting to see how Mrs. Haley fared in New Hampshire before deciding on a “major gift” to the Haley campaign, the FT reported, adding that he does not want to “throw money down a rat hole.”