The Clinton campaign had hoped to use the coming weeks to do everything they could to shed that image and convince voters that Mrs. Clinton can be trusted. Instead, they must contend with a damaging new report by the State Department’s inspector general that Mrs. Clinton had not sought or received approval to use a private email server while she was secretary of state.

It is not just that the inspector general found fault with her email practices. The report speaks directly to a wounding perception that Mrs. Clinton is not forthright or transparent…

Mrs. Clinton has long contended that voters care more about issues — like equal pay for women, widely available child care, and making college more affordable — than how she handled her emails as secretary of state. Even her Democratic primary opponent, Senator Bernie Sanders of Vermont, tried to squelch the storm over the private server during the first Democratic debate last fall.

But something has seeped into the electorate. A presidential campaign always contends with incoming fire, but it is also designed to serve as an infomercial to present a candidate’s best attributes. Instead, Mrs. Clinton has gone from having a 69 percent approval rating and being one of the most popular public figures in the country when she left the State Department in 2013 to having one of the highest disapproval ratings of any likely presidential nominee of a major party.