populist leader

The other, he says, is "perpetuating a state of crisis" - and always seeming to be on the offensive.

"A populist leader who gets into power is 'forced' to be in a permanent campaign to convince his people that he is not establishment - and never will be," according to Prof Nadia Urbinati from Columbia University.

She argues that populist content is "made of negatives" - whether it is anti-politics, anti-intellectualism, or anti-elite. Here lies one of the populism's strengths - it is versatile.

It is "extraordinarily powerful because it can adapt to all situations," she said.

Another common thread among populist leaders is they tend to dislike the "complicated democratic systems" of modern government - preferring direct democracy like referendums instead, according to Prof Bull.

That also ties in to its links to authoritarianism, he argues - a lack of trust in the established system gives rise to "strongman" leaders.

"Ultimately, the leader makes the decision in a way that just isn't possible in traditional democracies," he says.