Washington (CNN) A majority of American voters think Hillary Clinton's emails should be subject to a criminal investigation, a Monmouth University poll out Wednesday has found.

The numbers -- 52% of registered voters, including 82% of Republicans, 54% of independents and 23% of Democrats -- show that the Democratic presidential frontrunner's use of a personal email address on a private server during her tenure as secretary of state continues to be damaging.

They were asked: "Do you think Hillary Clinton's emails should be subject to a criminal investigation for potential release of classified material, or not?"

The survey was conducted July 21-Aug. 2, before Clinton's campaign announced it would turn over her server to the Justice Department in an effort to blunt an expanding probe.

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