Public Policy Polling, which I believe is one of the most accurate polling organizations around, reports that their latest South Carolina poll continues to show Donald Trump with a wide lead in the state. He's at 35% to 18% each for Ted Cruz and Marco Rubio, 10% for John Kasich, and 7% each for Jeb Bush and Ben Carson.
However, PPP notes that the race is still pretty fluid in South Carolina- 29% of voters say they might change their minds between now and Election Day. Trump benefits from having supporters who are pretty resolute though- 77% of them say they will definitely vote for him, compared to 76% for Cruz and 62% for Rubio. Among voters who say their minds are completely made up, Trump's support goes up to 40% to 20% for Cruz and 16% for Rubio.
On the Democratic side, PPP reports. Hillary Clinton leads Bernie Sanders 55/34. South Carolina exemplifies the way in which the Democratic race changes in places where there's a large African American electorate. Clinton and Sanders are tied with white voters at 46%, pretty similar to how the race played out in Iowa. But among African Americans Clinton continues to have a substantial advantage over Sanders at 63/23. Clinton is very popular among black voters with a 71/12 favorability, while feelings about Sanders continue to be pretty mixed with him coming in at 39/33.