The former president made multiple posts on his social media platform Truth Social on Tuesday and Wednesday, following his decisive win at the Iowa caucuses, and ahead of their next clash in New Hampshire next week.
Many of the posts included graphics of Ms Haley, calling out her previous statements and blasting her performance in the Iowa caucuses, where the former governor of South Carolina finished in third place, behind Mr Trump and Ron DeSantis respectively.
In one post, Mr Trump shared an image of a picture of Hillary Clinton – who he beat in the 2016 presidential race – with Ms Haley’s face crudely photoshopped over the top. The text at the bottom read “Haley” instead of “Hillary”.
Though the post contained no other text, the comparison appeared to draw on previous criticisms of Ms Haley from her GOP presidential candidate nominees, including branding her as a “neo-conservative” or “neo-con”.
Ms Haley strengthened her presidential resume with her stint at the United Nations, and remains a champion of Nato and support for Ukraine in fighting back against the full-scale Russian invasion that started in February 2022.
During a fiery GOP candidate debate in December, Vivek Ramaswamy seemed to compare Nikki Haley to former vice president Dick Cheney. “You can put lipstick on a Dick Cheney – it is still a fascist neocon,” he said.
Mr Ramaswamy, who has since dropped out of the race and endorsed Mr Trump, was explicit in saying he would seek to allow Russia to keep conquered Ukrainian territory, while Mr DeSantis has largely avoided discussing the crisis in detail.
Mr Trump himself has repeatedly been ambivalent on Nato, leading some observers to fear he could either pull the US out of the defence organisation or weaken it by refusing to commit to Article 5, which stipulates that an attack on one member of Nato constitutes an attack on all members.
He has also said he would solve the Ukraine crisis "in one day", which has been interpreted as forging a deal that would reward Vladimir Putin – whom Mr Trump has repeatedly praised – for his aggression.
Ms Haley has also come under fire from her GOP rivals – notably Mr Ramaswamy – for allegedly being corrupt, and only campaigning for the benefit of her donors. In November it was reported that Ms Haley and the CEO of JPMorgan Chase had been privately talking about the economy.
Similar accusations of corruption were made by Mr Trump towards Ms Clinton during their 2016 showdown, with the former president coining the now infamous nickname “Crooked Hillary”.
Elsewhere during Mr Trump’s rantings on Tuesday, the former president addressed Ms Haley by her given name Nimarata – though he spelt it incorrectly – in what appeared to be another racially charged attack on his former ambassador.
He wrote: “Anyone listening to Nikki ‘Nimrada’ Haley’s wacked out speech last night, would think that she won the Iowa Primary. She didn’t, and she couldn’t even beat a very flawed Ron DeSanctimonious, who’s out of money, and out of hope.
“Nikki came in a distant THIRD! She said she would never run against me, “he was a great President,” and she should have followed her own advice. Now she’s stuck with WEAK POLICIES, and a VERY STRONG MAGA BASE, and there’s just nothing she can do!”
Mr Trump has previously claimed that Ms Haley is not eligible to serve as president of the United States, using similar racist smear tactics he has previously deployed against former president Barack Obama and Vice President Kamala Harris in recent years.
The former president shared an article from far-right conspiracy site The Gateway Pundit which posited that Ms Haley is not a “natural born citizen” because her parents, Indian immigrants, were not American citizens when she was born in 1972.
Ms Haley was born in the United States.