Most Americans disagree with FBI Director James Comey's decision to recommend against charging Hillary Clinton with a crime as a result of her classified email scandal, new poll numbers show.

An ABC News/Washington Post survey published Monday morning found 56 per cent of adults in the U.S. believe it was a mistake not to prosecute the former secretary of state for mishandling state secrets by hosting them on a private, unprotected email server during her years in office.

The disappointed masses include 3 out of 10 Democrats – likely stacked with supporters of Vermont Sen. Bernie Sanders, who is expected to end his White House run and endorse Clinton on Tuesday.

LOSING GROUND: Hillary Clinton should have been prosecuted for mishandling classified documents as secretary of state, according to a majority of Americans who spoke with ABC News pollsters

WORRIED: Nearly 3 out of 5 Americans said Clinton's judgment makes them concerned about how she would behave as president

Just 35 per cent of Americans approve of the decision to close the embarrassing chapter of Democratic Party history without a criminal charge.

A sizable 57-percent majority say the email scandal makes them 'worried' about how Clinton might behave as president.

And 28 per cent of Americans now say the unprecedented episode has made them les likely to vote for Clinton in November. That includes one out of 10 Democrats.

Clinton has long been dogged by questions about her honesty and character.

During most of the Democratic primary season, she trailed Sanders by 20 points or more on measures of who was more 'honest and trustworthy.'

In some polls she has also fallen behind Republican rival Donald Trump on the same question.

Political independents, the all-important swing voters, sided with Republicans on the question of whether Clinton should have been charged with a crime.

Roughly six in 10 said the FBI was wrong to close the email case, and that the messy situation raises worries about what kind of president Clinton would be.

Among those independent voters who say the Clinton's email situation will affect their vote, a large majority swung away from her.

One-third of independents who say they are less likely to support Clinton now, compared with 5 per cent who say they are more apt to vote for her because of it.