The former South Carolina governor Nikki Haley has pulled within four percentage points of frontrunner Donald Trump in New Hampshire’s 2024 Republican presidential primary, a contest which could prove closer than expected for the ex-president, according to a new poll.

In an American Research Group Inc poll released on Thursday which had asked voters whom they preferred in the New Hampshire primary scheduled for 23 January, Haley earned 29% support to Trump’s 33%. That meant the gap between Haley and Trump was within the survey’s 4% margin of error after the former president had long held dominating polling leads in the race for the 2024 Republican White House nomination.

Haley’s strong showing in the American Research Group Inc survey came a day after a poll from the Saint Anselm College New Hampshire Institute of Politics found she had doubled her support in the state since September, seemingly cementing her as a clear alternate choice to Trump for conservative voters. The Saint Anselm survey’s findings were more favorable to Trump, however, showing him with a 44% to 30% lead over Haley.

But while Haley still has ground to gain to take the lead in the state, Trump coming in at less than 50% support “shows he has serious competition in the party”, the University of New Hampshire survey center director, Andrew Smith, has previously told USA Today.

Haley’s strong poll showings appear to have drawn a mixed reaction from Trump, who is separately contending with more than 90 criminal charges as he seeks a second presidency.

On one hand, he went on his Truth Social site on Friday and insulted Haley with his preferred nickname for her, writing: “Fake New Hampshire poll was released on Birdbrain. Just another scam!” He additionally spoke with the rightwing radio show host Hugh Hewitt on Friday and dismissed the polls showing Haley performing well against him as “fake” and insisted he was untroubled by her as a potential primary contender.

Yet citing two sources familiar with the conversations, CBS News reported on Friday that Trump had also simultaneously been asking his team about tapping Haley to serve as a vice-presidential candidate if he eventually wins the Republican primary to be the 2024 Oval Office nominee, which if accurate would be a sign that he covets capitalizing on her support. CBS said its sources had indicated the far-right reaction to a Trump-Haley ticket has been negative, however.

Haley for now has been touting her recent polling performances.

“Donald Trump has started to attack me,” Haley said at a campaign town hall on Wednesday in Iowa, where the caucuses that customarily kick off presidential election years are scheduled for 15 January. “He said, ‘I don’t know what this Nikki Haley surge is all about.’ Do you want me to tell you what it’s about? … We’re surging.”

Haley was the US ambassador to the United Nations after Trump won the presidency in 2016, but she resigned in 2018. Prior to that, she was governor of South Carolina from 2011 to 2017.

One of her more prominent acts as South Carolina governor was signing into law a ban on abortion which contained no exceptions for rape or incest. That ban took effect, along with similar ones in other states, after the US supreme court last year eliminated the federal right to abortion which had been established by the landmark Roe v Wade decision.

Trump, for his part, faces 91 criminal charges accusing him of trying to forcibly reverse his defeat to Joe Biden in the 2020 presidential election, illegally retaining government secrets after he left the Oval Office and illicit hush-money payments to the adult film actor Stormy Daniels.

He has also grappled with civil litigation over his business practices and a rape allegation deemed “substantially true” by a judge.

Trump more recently has been on the defensive against resurfaced claims that he kept writings by Adolf Hitler – the Nazi leader who orchestrated the murders of 6 million Jews during the Holocaust – by his bed.

Academics, commentators and political opponents have been quick to link Trump’s recent remarks that certain immigrants were “poisoning the blood of” the US to rhetoric used historically by Hitler, Benito Mussolini and other authoritarian world rulers.

“I know nothing about Hitler,” Trump said to Hewitt on Friday. “I’m not a student of Hitler.”

He then implied having at least some familiarity with Hitler’s sayings in regards to purity of blood.

“They say he said something about blood,” Trump told Hewitt. “He didn’t say it the way I said it, either, by the way. It’s a very different kind of statement.”