There's a chance US Republican candidate Nikki Haley's momentum may "run out of gas" after a recent gaffe, says former White House chief of staff Mick Mulvaney.
"This past week she got asked a relatively simple question, you expect to get questions when you run in this country about the causes of the Civil War," Mr Mulvaney told Sky News Australia.
He said in her answer she did not mention the word "slavery" at all.
"Even when the person came and asked a follow up question, she did not use the word slavery.
"And then after the interview, she accused that person asking the question of being a 'Democrat plant'.
"It was very, very poorly handled."
