Image copyright Getty Images Image caption Many Republicans say they want to see Hillary Clinton jailed

The chants of "Lock her up" directed at Hillary Clinton have been a nightly feature of the Republican convention in Cleveland. Is that fair enough or a new political low?

Many of the speakers have focused more on the faults of Hillary Clinton than the virtues of Donald Trump.

New Jersey Governor Chris Christie read out a list of alleged "crimes" by Mrs Clinton, the presumptive Democratic nominee, and asked the crowd if she was guilty. His baiting of the crowd resulted in chants of "Lock her up!"

The same slogan has been repeated each night, most recently when Mr Trump gave his big speech on Thursday.

Much of the criticism from the stage, from Mr Christie and others, was about Mrs Clinton's use of a private email account while she was serving as secretary of state.

An FBI investigation said she was "extremely careless" but found her actions didn't warrant criminal prosecution.

Mr Christie also questioned her "selfish, awful judgement" which was to blame for various foreign policy problems in Libya, Syria and elsewhere.

Image copyright AP Image caption New Jersey Governor Chris Christie was one of the first mainstream Republicans to declare support for Mr Trump

The divisive and at times ugly rhetoric - a charge directed at both sides during the campaign - is not particularly shocking to long-time political observers, but some say it is worse than ever.

Norm Ornstein, a resident scholar with the American Enterprise Institute, speaking from Cleveland, said this election is the ugliest he has ever seen in the US.

"You expect a tough rhetoric against the opposition," Mr Ornstein said. "You don't expect a convention hall that has its major theme as not what your nominee will do but an enormous level of bile towards the other opponent."

He also said he would not expect primetime speakers to encourage that "bile" but Mr Christie, former candidate Ben Carson and radio host Laura Ingraham had done that, in his view.

"It makes absurd the notion you're trying to unite the government and not divide it," he said.

Analysis - Katty Kay, BBC News, Cleveland

I honestly don't know if it's because Hillary is a woman or because she's been around as a political figure for so long or because her email server makes her look like she thinks she's above the law but the hatred of her here is vicious and visceral.

This has become the "lock her up" convention. Ask individual delegates about Hillary and they get a glint in their eye - she's "evil", a "liar", "dangerous".

Chris Christie's mock prosecution whipped up a crowd that was willing to be pulled into the fringes of political acceptability. Think what you will of Hillary Clinton as a potential president, there's a nasty mood here when it comes to her. You see it in the slogans, the T-shirts, the buttons and the speeches.

On the whole this convention is more subdued than any I have been to. There's a lack of excitement and the only thing the party really seems united about in Cleveland is the other party's nominee. They really, really hate her. On that they can agree.

Political commentators and journalists took note of this new tone from the convention floor.

James Fallows, a correspondent for the Atlantic, tweeted on Wednesday: "Seriously, we have NEVER seen this 'lock her up!' penal-system mania before".

Annie Karni of Politico noted that Minnesota Senator Al Franken called the "lock her up" chants "very banana republic".

Tough campaign rhetoric is nothing new, Mr Ornstein said. In 1972, Democrats said Richard Nixon was a war criminal for keeping US troops in Vietnam, and in 1996, people said Bill Clinton was not qualified to be president for being an adulterer.

However, that is "mild stuff" compared to what we are seeing at this year's RNC, he said.

Mass media consumption and social media that puts focus on shock value has only made it worse, he said.

"It's created a tribal political arena... and an encouragement of the most base and extreme forces in society. You can't say it's a shock we've gotten here, but it's a real worrisome thing."

Image caption Kendall Jessup from Texas said Mr Christie's tone was just right

But that's not a view shared by some of the delegates in Cleveland, who believe the chants are merely an expression of the fact there is one law for the Clintons and one law for the rest.

Kendal Jessup from Texas said Mr Christie's speech was just right and it united the arena.

"Suddenly everybody is on board, because everybody in the arena can agree that Hillary is not someone who can sit in the White House," she said.

"It was not too violent. It set the right tone. And it's not because she's a woman."

Image caption Nancy Elliot (pictured right) said Mr Christie 'nailed it'

Nancy Elliot, a Trump supporter from New Hampshire, said Mr Christie "absolutely nailed it" with his mock prosecution of Mrs Clinton.

"I've never seen a candidate with such a lack of integrity. What she did was criminal - and that's not exaggeration, that's a fact."

She added that the angry mood in the arena reflected the hostility the party faithful feel towards the Democrat. They wanted to make sure that came through loud and clear.

"It's the only chance to get traction with the whole Hillary story because our media is not going to present it again once the campaign starts."

Not everyone is happy with the tone of the convention - Cleveland resident and undecided voter Diana Borcz said she was "really disappointed".

"They're not talking about the party and the policies but kept referring negatively to her career and her family," she said. "There's not enough on what Trump will actually do."

And Senate majority leader Mitch McConnell told CNN that he disagreed with the "Lock her up" chant and disagrees that Mrs Clinton should go to jail.

Additional reporting from Anna Bressanin and Ben Bevington in Cleveland