05/06/2015 06:32 EDT | Updated 05/06/2016 05:59 EDT

Clinton campaign juggernaut still chugging along, despite a few new dents

WASHINGTON - Hillary Clinton's still unquestionably the favourite in the 2016 U.S. presidential race — despite the ethics controversies swirling around her family finances and her atypical email habits.

Some of her supporters have seized upon new polling data that confirms her front-runner status and pointed to it as evidence that the controversies are a non-issue.

But signs Wednesday suggested the dust has yet to settle.

One example occurred in the U.S. Congress. A witness from Clinton's former department testified in a hearing about her exclusive use of a home-based email server while secretary of state.

The employee called it wrong: "I think the message is loud and clear that that is not acceptable," said Joyce Barr, the State Department's chief freedom of information officer.

"We continue to do training but we sent department notices, telegrams, we've talked to directors."

Clinton has agreed to testify later this month at the request of the special committee investigating the Benghazi attacks. Her opponents want her to hand over her private email server — something she's refused to do.

Scratch the surface of the surveys, and even the poll proclaiming Clinton the front-runner contain cautionary notes. That's true of an NBC survey that placed her three points ahead of her closest Republican rival, Sen. Rand Paul, and six points ahead of her next-closest challengers Jeb Bush and Sen. Marco Rubio.

That same survey found only 25 per cent of respondents considered her honest and straightforward, down from 38 per cent last year. Her net favourability rating was zero, meaning the same number of people professed to like and dislike her — down from the whopping plus-31 per cent she enjoyed in early 2013.

A New York Times poll was more flattering. It found 48 per cent of respondents saw her as honest, while 45 per cent did not — which is up from a month earlier.

But even that poll suggested public opinion hasn't settled. The most popular answer selected by respondents, by far, when asked whether Clinton's decisions as secretary of state might have been influenced by donations to her family foundation, was: "Don't know enough."

Eighteen months of attack ads and congressional grillings from the Republican party will seek to shape those still-unformed opinions. Her family charity and her private email server are already a staple of her opponents' stump speeches.

Different ethics-in-government experts contacted Wednesday said they haven't heard anything illegal in the revelations emanating from the book, "Clinton Cash."

The book describes how the family charity took in donations, and Bill Clinton received lucrative speaking fees, from foreign interests that had business interests before the U.S. government.

One said there's nothing unlawful in taking donations from someone who wants to curry favour with you — not unless a specific decision has been requested in return.

Peter Henning said he regrets that the law isn't stricter, but that it's common practice in U.S. politics and the jurisprudence set out in the Supreme Court's Sun-Diamond decision.

"Ethics is not morality," said Henning, a professor at Wayne State University Law School who specializes in government ethics and has written a book on public corruption.

"Is it right that a former president can cash in when his wife becomes secretary of state? You put it in those terms, the answer is no. This is not how government and society should operate. (But) that's not going to stop it from happening."

The former president, asked about the controversies, said he's not aware of ever having been given money to influence a decision. Bill Clinton defended himself, and the work of his foundation, in interviews with NBC during a trip through Africa.

"There is no doubt in my mind that we have never done anything knowingly inappropriate in terms of taking money to influence any kind of American government policy," Clinton said this week.

He called it a double-standard — Clintons get judged for taking speaking fees and charitable donations, but not their opponents.

As for whether he'll keep accepting paid speaking engagements, he said: "Oh, yeah. I've gotta pay our bills."