Donald Trump is aiming for a commanding victory in New Hampshire, securing a sweep of the first two Republican primary races that would make a November rematch with US president Joe Biden look more likely than ever.

The biggest question is whether Mr Trump’s last major rival, former UN ambassador Nikki Haley, will be able to eat into his margin — or pull off an upset outright.

Ms Haley has dedicated significant time and financial resources to New Hampshire, hoping to appeal to its famously independent-minded electorate.

In the first results released early on Tuesday, all six registered voters of the tiny resort town of Dixville Notch had cast their ballots for Ms Haley over Mr Trump. The town is the only one in New Hampshire this year that opted to vote at midnight.

Mr Trump won New Hampshire’s Republican primary during his first run for president in 2016, but some of his allies lost key races during the midterms two years ago.

Ms Haley also has to contend with an opponent who has a deep bond with the Republican base and has concentrated on winning the state decisively enough that it would effectively end the competitive phase of the primary.

If successful, Mr Trump would be the first Republican presidential candidate to win open races in Iowa and New Hampshire since both states began leading the election calendar in 1976 — a clear sign of his continued grip on the party’s most loyal voters.

Mr Trump’s allies are already pressuring Ms Haley to leave the race and these calls will intensify if he wins New Hampshire easily.

Were she to drop out, that would effectively decide the Republican primary on its second stop, well before the vast majority of Republican voters across the country have been able to vote.

Ms Haley has been campaigning with New Hampshire’s popular Republican governor, Chris Sununu, a Trump critic.

She insists she is in the race for the long run, telling supporters in Franklin on Monday that “America does not do coronations”.

“This is about, do you have more of the same, or do you want someone who’s going to take us forward with new solutions,” Ms Haley told reporters, also saying that: “We can either do the whole thing that we’ve always done and live in that chaos world that we’ve had, or we can go forward with no drama, no vendettas and some results for the American people.”

“This is a two-person race,” she added.

Ms Haley and Mr Trump were both hoping to capitalise on high-profile recent departures from the race.

Ms Haley could get a lift from some supporters of former New Jersey governor Chris Christie, who campaigned around decrying Mr Trump but ended his bid shortly before Iowa’s caucus last week.

Meanwhile, Mr Trump may be able to consolidate support from conservative voters who were supporting Florida governor Ron DeSantis, who dropped his White House bid on Sunday.

Mr Trump, who appeared at a pre-primary rally in Laconia with one of his former primary rivals, South Carolina senator Tim Scott, was already looking ahead to being the race’s last Republican candidate.

Asked during an interview on Monday with Newsmax about Ms Haley possibly abandoning her campaign after New Hampshire, the former president said he would never call on her to do that but added: “Maybe she’ll be dropping out Tuesday.”