The Democratic Party race to take on US president Donald Trump has moved to the South, where the African-American vote comes into play for the first time.

The seven candidates debating in South Carolina included front-runner Senator Bernie Sanders, former vice-president Joe Biden and billionaire Mayor of New York, Mike Bloomberg.

Sanders came under sustained attack from other leading contenders during the latest candidates' debate, ahead of Super Tuesday.

USSC associate professor Brendon O'Connor was interviewed on ABC Radio's RN Drive.