Time is running short for Haley, who served as Trump's ambassador to the United Nations, to topple the Republican presidential frontrunner after his victory in the Iowa caucuses underscored his dominance in the primary race.
If she cannot score an upset win in New Hampshire on Tuesday, her already narrow path to the nomination could close altogether.
This was truly a birthday I'll never forget! I can't thank everyone enough for making it so special. �🇺🇸�� — Nikki Haley (@NikkiHaley) pic.twitter.com/jmmlVIVWlEJanuary 21, 2024
Trump, who is leading Haley and Florida Governor Ron DeSantis in New Hampshire, addressed a stadium of cheering supporters in Manchester on Saturday night, encouraging them to vote in the primary poll on Tuesday.
But he also appeared to shift some of his focus to the next major nominating contest, in South Carolina in late February.
At the rally, several high-ranking state and federal officials from that state spoke on Trump's behalf, including South Carolina Governor Henry McMaster.
"They understand that I am the only candidate in this race who is going to save America and we're gonna get rid of this Biden disaster right away," Trump said.
"So you know what I'm doing?
"I'm kissing ass."
Haley has stepped up her attacks on Trump in recent days, drawing contrasts with a businessman and politician whose time in the White House was characterised by chaos and who faces four criminal cases, including for his efforts to overturn the results of the 2020 election that he lost to now President Joe Biden.
Despite her shift, some Republican and independent voters say Haley should go further with her criticisms and that she has not hit her main rival hard enough throughout her campaign.
Nikki Haley has criticised Donald Trump for his affinity with strongmen such as Vladimir Putin. (AP PHOTO)
"I think Trump needs to be put in his place," said Chris Jay, 57, a Republican who said he was leaning toward Haley but wanted her to lob more head-on attacks at the former president.
Haley on Saturday knocked Trump, 77, for his age after he seemingly confused her with former Speaker of the House of Representatives Nancy Pelosi.
Haley also criticised Trump for his affinity with strongmen such as Russia's Vladimir Putin and North Korea's Kim Jong-un.
Trump, she said at a campaign event in Keene, New Hampshire, on Saturday, "needs to stop praising dictators".
She said as his UN ambassador, she tried to break up his "bromance" with Putin.
Trump has upped his already fierce attacks on Haley as well, targeting her given first name on his social media platform and amplifying false posts questioning her birthright US citizenship.
The daughter of two immigrants from India, Haley was born Nimarata Nikki Randhawa but has long used her middle name Nikki and later took her husband's surname.
At the Saturday night rally in Manchester, Trump attacked Haley for her support among some wealthy donors who have also supported Democrats and called her a threat to social security.
Above the stage where Trump spoke, a large screen showed messages critcising Haley, alongside unflattering pictures of her.
"Nikki Haley is loved by Democrats, Wall Street and globalists," one of the images on the screen read.
