Republican presidential candidate Donald Trump said he would release his tax returns if Democrat Hillary Clinton publishes the more than 30,000 emails that were deleted from her private email server when she was secretary of state.

Trump so far has refused to release his returns -- a break from decades of precedent -- because of an audit. But Trump said he would go against the advice of his lawyers if Clinton acts first.

"My lawyers they say don't do it ... I would go against them if she releases her emails," said Trump, drawing cheers from the audience, which was supposed to stay silent during the debate.

Clinton said she made a "mistake" using the private email server as secretary of state. "I take responsibility for that," she said, before refocusing on Trump's taxes.

"It just seems to me that this is something that the American people deserve to see," she said. "And I have no reason to believe that he's ever going to release his tax returns because there's something he's hiding. We'll keep guessing what it might be that he's hiding."

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