The video will start in 8 Cancel

What is really going on in politics? Get our daily email briefing straight to your inbox Sign up Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

What would be the hottest topic of the first live US Presidential TV debate?

Taxes, jobs, how to combat ISIS?

No, so far it is Donald Trump's sniff.

The Republican candidate took to the match up with typical gusto, launching a series of tirades against 'Mexico', 'politicians like Secretary Clinton' and doing things 'bigly'.

(Image: AFP/Getty Images)

(Image: AFP/Getty Images) (Image: Getty)

But the millions watching around the world could not help but be mesmerised by Trump's strange sniffs in between points.

Some suggested the sniff is a nervous tic, others said Trump sniffed after making a particularly satisfying point.

Either way, it quickly became the most popular topic of the Presidential debate on Twitter.

And of course, the inevitable parody Twitter account quickly came into existence '@TrumpSniff'.

More than 100m people are thought to be watching the debate in the US alone tonight.

It’s thought they will be a key factor in swaying undecided voters to one candidate or the other.

Questions over Hillary Clinton’s health have dogged her campaign in recent weeks, after she admitted a diagnosis of pneumonia.

She’ll be hoping Donald Trump will seem oafish and unpresidential during the debate - which will be the first time many Americans will see him talking politics for an extended period of time.

But the Donald is nothing if not a showman - will his brash, reality TV style impress floating voters enough to choose him for Commander in Chief?