Either way, the highly anticipated second debate between US presidential candidates Hillary Clinton and Donald Trump, delivered softer than expected audience numbers.

Their first clash between the political rivals drew a television audience of 84 million in the US.

Inclusive of online streaming that figure set a total audience record of more than100 million viewers.

Their second debate, fuelled by intense media attention on crude remarks Trump made about women in a decade-old clip, drew just 68.8 million viewers.

In context, those are still extraordinary numbers.

And though they represent a drop, that drop is just around 18 per cent.

Anecdotal evidence suggests the promise of a nasty exchange between the candidates, initially seen as a drawcard, might have been a turn-off, particularly for families.

In the US a total of 10 channels carried the second debate, down from 13 channels which carried the first debate.

One of the channels which did not carry the debate was the network NBC, which aired Sunday Night Football instead.

NBC's absence from the road-blocked broadcast would have been a kick in the shins for the ratings numbers; NBC's telecast of the first debate was the most watched with 18.2 million viewers.

The absence of NBC also saw the news cable networks which carried the debate lift their audiences significantly, notably CNN.

The debate was moderated by CNN's Anderson Cooper and ABC's Martha Raddatz.

In historical terms, second debates – there are traditionally three – have smaller television audiences than first debates.

And Hurricane Matthew, which is affecting the south-eastern United States, would have disrupted television viewing in those areas.

The first debate between Clinton and Trump entered the record books as the most watched presidential debate in history.

It beat the previous record holder, the 1980 debate between Jimmy Carter and Ronald Reagan, which drew 80 million viewers, and was broadcast in an era where only a few channels broadcast presidential debates.

In a powerful demonstration of the focus on the presidential candidates, at the expense of everything and everyone else, the vice-presidential debate delivered a ratings low.

The debate between vice-presidential candidates Tim Kaine and Mike Pencem drew an audience of just 37 million.