Nikki Haley, the Republican presidential candidate in the US elections, said this is not "the end of her story" despite Donald Trump's easy win in the South Carolina primary, her home state, where the former governor long suggested her competitive ability with the former president would show.

In defiance of calls from Republicans in South Carolina to exit the race, Haley planned to travel on Sunday to Michigan, which holds its primaries on Tuesday.

With his win on Saturday in the first southern contest, Trump has now swept all primaries or caucuses on the early Republican calendar that award delegates. His performance left little room for maneuver for Haley, his former ambassador to the United Nations.

Trump said at a victory night rally in Columbia: "I have never seen the Republican Party as united as it is now."

Haley insists she is sticking with it despite mounting pressure to drop out and allow Trump to focus fully on Democratic President Joe Biden in a 2020 rematch.

In addition to the large rally in vote-rich Oakland County, Michigan, northwest of Detroit on Sunday evening, she scheduled a Monday event in Grand Rapids, the Republican hub of western Michigan.

Haley told her supporters on Saturday: “I’m grateful that today is not the end of our story.” "We will keep fighting for America and will not rest until America wins."

Asa Hutchinson, one of Trump’s critics and former Arkansas governor who dropped out of the Republican presidential race after the Iowa caucuses in January, said on CNN's "State of the Union" program that he believes Haley should stay in. He added: "The challenge is she did all she could in South Carolina." 

Haley pledged to continue at least through the March 5 primaries, known as Super Tuesday, and Hutchinson said "things need to pick up because you’re hitting the delegate wall," so she has to prove herself.

Leading Republicans in South Carolina stood with Trump, including US Representative Nancy Mace, who endorsed him last week.

For US Representative Russell Frye, "This was always a primary in name only" and Trump was never at risk of losing to Haley. Frye said Trump will be the Republican nominee and recent election results were "just further confirmation of that."

Texas Governor Greg Abbott, an ally of Trump, said Trump was on track to secure the nomination by mid-March, "I would say the winds are strong at his back."

Not all voters in South Carolina want Haley to end her campaign.

Irene Solkowski from Daniel Island said she hopes Haley continues to work, suggesting the former governor would be a more appealing candidate in the general election than Trump despite his popularity among the Republican base that drives the primary season.

Solkowski, an accountant, said: "They’re not thinking: who do you want to represent us in the general election? They need to see longer."