Donald Trump continues to maintain a substantial lead in South Carolina with only four days left until the state's Republican primary takes place, according to a new poll.

According to the latest CNN poll, the billionaire real estate mogul leads with 38 percent support, giving him a 16-point lead over Sen. Ted Cruz (22 percent), who he has been relentlessly attacking in recent days.

Following up the pair are Sen. Marco Rubio with 14 percent backing and former Florida Gov. Jeb Bush with 10 percent. Dr. Ben Carson and Ohio Gov. John Kasich round out the field with six percent and four percent, respectively.

Buoying Trump's lead with Palmetto State voters are concerns regarding the economy, immigration and ISIS — all of which are categories where Trump tops the GOP field. In addition, voters also believe he has the best chance to beat the Democratic nominee in November.

Overall, according to the RealClearPolitics average, Trump leads Cruz and Rubio in the state with 36.6 percent support. Cruz and Rubio continue to battle for second, with the Texas senator leading his upper chamber colleague 18.4 percent to 15.6 percent.