Mr. Trump has reinvigorated explicit appeals to ethnocentrism, and some voters are responding.

Data from Public Policy Polling show that a third of Mr. Trump’s backers in South Carolina support barring gays and lesbians from entering the country. This is nearly twice the support for this idea (17 percent) among Ted Cruz’s and Marco Rubio’s voters and nearly five times the support of John Kasich’s and Ben Carson’s supporters (7 percent).

.. The P.P.P. poll asked voters if they thought whites were a superior race. Most Republican primary voters in South Carolina — 78 percent — disagreed with this idea (10 percent agreed and 11 percent weren’t sure). But among Mr. Trump’s supporters, only 69 percent disagreed. Mr. Carson’s voters were the most opposed to the notion (99 percent), followed by Mr. Kasich and Mr. Cruz’s supporters at 92 and 89 percent. Mr. Rubio’s backers were close to the average level of disagreement (76 percent).

.. According to P.P.P., 70 percent of Mr. Trump’s voters in South Carolina wish the Confederate battle flag were still flying on their statehouse grounds. (It was removed last summer less than a month after a mass shooting at a black church in Charleston.) The polling firm says that 38 percent of them wish the South had won the Civil War. Only a quarter of Mr. Rubio’s supporters share that wish, and even fewer of Mr. Kasich’s and Mr. Carson’s do.

.. Nationally, further analyses of the YouGov data show a similar trend: Nearly 20 percent of Mr. Trump’s voters disagreed with Abraham Lincoln’s Emancipation Proclamation, which freed slaves in the Southern states during the Civil War. Only 5 percent of Mr. Rubio’s voters share this view