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The town hall debate between Hillary Clinton and Donald Trump turned ugly very quick, with each candidate hurling attacks based mostly on previous issues that had been a part of a campaign that seems like it has been going on for forever.

But Trump launched something very new on Sunday, something that many people feel crossed a line.

SEE ALSO:Trump lurks like a hungry ghost behind Clinton during entire debate

During one particularly contentious exchange, Trump pledged that if he won the presidency, he would appoint a special prosecutor to investigate Clinton's use of a private email system during her time as the secretary of state.

"You'd be in jail," Trump said to Clinton.

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The moment came and went relatively quickly, with numerous other moments gaining plenty of attention.

The pledge, however, stuck with many as a particularly terrifying statement.

Former attorney general Eric Holder weighed in, noting that Richard Nixon attempted a similar maneuver -- an action that resulted in the resignation of his attorney general.

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Trump's campaign felt the moment was strong enough to tweet out.

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Plenty of other politics watchers also noticed the moment.

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BONUS VIDEO: Watch Trump lurking behind Clinton during the debate.

TopicsElections