Image copyright AP Image caption A party divisions have been on display for a national audience

This is my seventh US political convention and I have never seen anything quite like this.

I've never heard a speaker booed on the stage or a party this beset by internal strife or a wing of a party drag the rest out to the fringes of political respectability. It's stunning and begs the question: Are we watching the death throes of the Republican Party?

Many people around the world may be surprised that the most vocal challenge to Donald Trump comes not from the American political centre but from the right of the Republican Party. Ted Cruz is a Christian conservative who opposes Donald Trump for being too liberal and he is the one who's stood up and made a big stink at Mr Trump's coronation party.

Mr Cruz is right, of course: on economic issues Mr Trump is liberal by the standards of the Republican Party.

But it's noticeable that the objection to Mr Trump in Cleveland is definitely not because of some of the more contentious things he has said about Muslims or Mexicans or women. There's barely a squeak of complaint about those things here in Cleveland. Indeed, in some ways the delegates at this convention seem to have gone beyond even Mr Trump on politically extreme rhetoric.

The subject of their ire is Hillary Clinton.

Image copyright Reuters Image caption Mrs Clinton, not Mr Trump, has united the Republican Party faithful

Image copyright Getty Images Image caption 'Lock Her Up!' is a common refrain at this year's convention

It's normal for conventions to spend time attacking the nominee of the other party. And in some recent conventions the tone of those attacks has become more personal. In 2004 Democrats were really angry with President George W Bush and the Iraq war. In 2012 Republicans clearly hated the way President Barack Obama had expanded the role of American government. But even then it didn't feel like this.

I honestly don't know if it's because Mrs Clinton is a woman. It may be 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 Mrs Clinton and they get a glint in their eye - she's "evil", a "liar", "dangerous."

New Jersey Governor 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 Mrs 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.