Donald Trump has predicted he will “win big” tonight in Nikki Haley’s home state of South Carolina, as the last Republican voters in the state cast their ballots.

The Trump campaign is expecting its fourth major win of the primary, after the former president swept to victory in Iowa, New Hampshire and Nevada.

Speaking at the Conservative Political Action Conference (CPAC) near Washington, DC on Saturday, Mr Trump told a crowd he was leaving to give a speech after the polls close.

“Now I’m going to the place I’m supposed to be,” he said, urging Republicans to “go out and vote please”. He added: “We’re going to win big.”

A loss for Ms Haley in South Carolina could spell the end of her campaign, although she has vowed to fight on in the face of Mr Trump’s commanding poll lead.

Philip van Scheltinga, a pollster at Redfield and Wilton Strategies, told The Telegraph there was “no coherent strategy for staying in the race” and “no point” fighting on if she loses.

Polls close at 7pm Eastern Time (12am GMT) and results are expected shortly afterwards.