GOP poll leader Donald Trump came out swinging against Democrat Hillary Clinton on Sunday, criticizing her use of a private email server while she was secretary of state.

Trump went on the offense against Clinton. He likened her actions to those of Orange County native David Petraeus, whose scandal forced him to resign.

"She's the worst secretary of state in the history of our country," said Trump.

On Saturday, Clinton spoke of the email scandal that is threatening to follow her entire campaign.

"Let me first say, I am confident that I never sent nor received any information that was classified at the time it was sent and received," said Clinton. "What you're seeing here is a typical discussion, to some extent a disagreement among various parts of the government over what should or should not be publicly released."

Hillary Clinton has announced plans to testify before the House committee investigating the deaths of four Americans in the 2012 attack on a diplomatic compound Benghazi, Libya.