North Carolina's primary is part of a Super Tuesday slate of 16 nominating contests that will bring Trump close to clinching the Republican nomination. It also is the only race that day that will be held in a battleground state that could decide the next occupant of the White House.
Trump edged President Joe Biden in North Carolina in the 2020 election by 1.3 percentage points - about 75,000 votes - the closest margin in any of the states that he won.
While Trump is heavily favored in North Carolina's primary on Tuesday, Haley's performance should give a sense of his vulnerabilities in the state, particularly among moderate and independent voters, said Thom Little, a professor of political science at the University of North Carolina-Greensboro.
The state's election rules allow independents who are not affiliated with a party to vote in the Republican primary.
Those voters have been a source of strength for Haley in states such as New Hampshire and South Carolina, where she scored about 40% of the vote.
Haley, a former U.S. ambassador to the United Nations under Trump, was scheduled to campaign in the Raleigh area on Saturday after visiting Charlotte on Friday evening.
Trump was expected to draw a much larger crowd for his rally on Saturday at a coliseum in Greensboro.
Haley has vowed to stay in the race past Tuesday, when 874 of the 2,429 delegates at play in the Republican primary will be up for grabs. Trump is expected to capture the vast share of them, and his campaign has projected he will secure the nomination by March 12 or the week after.
Voters who come out for Haley in North Carolina will have to decide in November whether to switch to Trump, stay home without voting or cross over to Biden, Little said.
Those voters would be targeted by both the Biden and Trump camps. Unaffiliated voters now make up a larger segment of the electorate in the southern state than registered Democrats or Republicans.
"It's a state where both parties are going to spend a lot of time," Little said. "And money."
The last Democratic presidential candidate to win the state was Barack Obama in 2008. Both the Biden campaign and the main super PAC backing it, Future Forward, have identified North Carolina as a priority along with other Sun Belt states such as Arizona and Georgia.
Early polls of a head-to-head matchup show Trump leading Biden in North Carolina.
In January, Future Forward said it would include the state in a massive $250 million battleground state ad buy ahead of the November election.
Biden traveled to North Carolina in January to trumpet infrastructure spending, and Vice President Kamala Harris discussed economic issues during a visit to the state on Friday.
Abortion has emerged as a key issue in North Carolina after the Republican-dominated state legislature last year largely banned the procedure after 12 weeks. The legislature overrode a veto of the measure by Democratic Governor Roy Cooper.
Cooper is leaving office after two terms, and the election to replace him this year is also expected to be hard fought.
(Reporting by James Oliphant. Additional reporting by Trevor Hunnicutt.; Editing by Colleen Jenkins and Deepa Babington)
By James Oliphant
