Miami - Donald Trump and other Republicans have for months floated the possibility that Democratic front-runner Hillary Clinton could face criminal charges for her role in the use of a private email server while serving as secretary of state.

At Wednesday's debate in Miami, she was confronted in the opening minutes about whether she would drop out if she was slapped with an indictment.

"Oh, for goodness - that is not going to happen," she answered to applause. "I'm not even answering that question."