Former US president Donald Trump has lobbed racially charged attacks at his Indian-American Republican rival Nikki Haley by repeatedly referring to her as “Nimbra", in an apparent intentional misspelling of her birth name.

Trump's attack against Haley, a daughter of Indian immigrants who served as his UN ambassador, comes days before a hotly contested New Hampshire primary that could determine the trajectory of the party’s presidential nomination contest.

Haley, 52, whose parents moved to the United States in the 1960s, was born Nimarata Nikki Randhawa.

The former South Carolina governor has long used her middle name Nikki and adopted the surname Haley after her marriage in 1996.

But Trump, 77, repeatedly referred to Haley as “Nimbra” in a rant on his Truth Social account, adding her to the list of foes he has targeted with racist attacks.

He also insisted she “doesn’t have what it takes” to be president.

Reminiscent of his spurious claims about former president Barack Obama’s citizenship, Trump also last week spread a false “birther” claim about Haley when he shared a post on Truth Social from the Gateway Pundit, a far-right website that propagates baseless accusations, The Washington Post newspaper reported.

The post falsely suggested Haley was ineligible to be president or vice president because her parents were not US citizens when she was born, it said.

The US Constitution states that a natural-born citizen can be president, and Haley automatically became a US citizen when she was born in South Carolina in 1972.

Trump's use of Haley’s birth name comes as the topic of racism has emerged as a flash point among Republicans on the campaign trail, with Haley recently asserting that the United States is not and never was a racist nation, the newspaper said.

Friday wasn’t the first time Trump has mocked Haley’s name. After the Iowa caucuses on Monday, Trump embarked on a tirade against Haley, misspelling her first name.

“Anyone listening to Nikki ‘Nimrada’ Haley’s whacked-out speech last night, would think that she won the Iowa Primary,” Trump wrote on Truth Social. “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!” DeSanctimonious is a Trump nickname for another Republican rival, Florida Gov Ron DeSantis.

Haley repeatedly stated that she has always gone by her middle name, which in Punjabi means “little one,” and that she changed her last name to Haley after marrying her husband, Michael Haley.

Trump, whose mother migrated to the United States from Scotland, has a history of using a rival’s name or background as a tool in his efforts to make rivals sound like they are not fully American.

During the 2016 presidential race, he referred to Senator Ted Cruz, who was then a Republican presidential candidate, by his first name, Rafael.

He also repeatedly mispronounced and drew out the first name of Kamala Harris, now the vice president, on the 2020 campaign trail.

Trump also built favour with the extreme right of the Republican Party when, in 2011, he began floating racist and baseless claims about Obama not being born in the United States, and he frequently emphasised Obama’s middle name, Hussein.

Civil rights leaders denounced Trump’s remarks as a racist appeal to White people, who make up more than 92 per cent of the population in New Hampshire, according to the latest census figures.

Elder James Johnson, head of the Racial Justice Network in South Carolina, said on Friday that Trump’s remarks are his way of saying “she is not one of us, that she is a Brown person, that she is not a White person.” By referencing the birth name Haley has not used in public life, Trump is “sending a message to white nationalists,” said Johnson, who offered that he is “not a fan” of Haley overall.

Another civil rights activist said the racism behind Trump’s behaviour is obvious.

“Why is he actually even using this name? What purpose does it serve?” asked Anthony Poore, president and CEO of the New Hampshire Center for Justice and Equity, a racial and social justice organisation.

Poore said Trump’s record — dating back to when he and his father were found guilty of housing discrimination against Black people, to attacks on Obama’s place of birth — makes clear what he is doing.

Asked Friday on the campaign trail if Trump’s attacks against her are racist, Haley said in New Hampshire that she would “let the people decide” what the former president means.

“He’s clearly insecure. If he goes and does these temper tantrums, if he’s going and spending millions of dollars on TV, he’s insecure, he knows that something’s wrong,” Haley said. “I don’t sit there and worry about whether it’s personal or what he means by it.” The attacks on Haley come as she has continued to defend the notion that the United States is not a “racist country” and has “never been a racist country.” “Are we perfect? No,” Haley said on Fox News on Tuesday. “But our goal is to always make sure we try and be more perfect every day that we can.” Haley’s father, Ajit Singh Randhawa, is a professor of biology who got his PhD at the University of British Columbia and later moved to Bamberg, a segregated town where Haley was born, to teach at nearby Voorhees College — a historically Black university.

Haley told Fox News that although she faced racism as a “Brown girl that grew up in a small rural town in South Carolina,” she became “the first female minority governor in history, who became a UN ambassador and who is now running for president.” “If that’s not the American Dream, I don’t know what is,” Haley continued. “You can sit there and give me all the reasons why you think I can’t do this. I will continue to defy everybody on why we can do this, and we will get it done.” In an interview with CNN, she acknowledged that America had its “stains” but said that “national self-loathing” was “killing” the United States.

“I want every Brown and Black child to see that and say, ‘No, I don’t live in a country that was formed on racism. I live in a country where they wanted all people to be equal, and to make sure that they had life, liberty and the pursuit of happiness,’” Haley said.

When asked about Trump repeatedly referring to Haley as “Nimbra,” Trump campaign spokesman Steven Cheung said in an email to The Washington Post, “Can you tell me how (Trump’s Truth Social) post would even be construed as racist?” When provided with a list of examples of how Trump has tried to “otherize” his foes by emphasising their race or background, Cheung added, “Sounds like those who take offence are engaging in faux outrage racism. They should get a life and live in the real world.”

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