An exciting new research project by the Guardian and Team Populism shows empirically what many have asserted and felt: the world is getting more populist. Professor Kirk Hawkins, from Brigham Young University in Utah, and 46 researchers analysed 728 public addresses by 140 presidents and prime ministers in 40 countries, in Europe and the Americas. This is the largest comparative project of this nature I am aware of, and a treasure trove for academics and journalists.

The study shows not just that the number of populist leaders has doubled, but that the average populist content of political leaders’ speeches has doubled too. Where political speeches were on average “not populist” in 2004, they are approaching “somewhat populist” today. To be clear, most of the political leaders studied were “not populist”, but that is to be expected of this particular subset of politicians, ie national leaders. Even today, populism is still primarily a feature of political challengers, who were not included in this study.

As expected, politicians that are broadly considered to be populist, such as the late Venezuelan president Hugo Chávez and Recep Tayyip Erdoğan, president of Turkey, scored highest on the populism scale (“very populist”), but some mainstream politicians scored “somewhat populist” too, such as the former Croatian prime minister Ivo Sanader and the former Latvian PM Einars Repše. Some have even come to use a discourse, at least occasionally, that is even more populist than some true populists’. The most striking example in the dataset is Theresa May’s speech to the 2018 Conservative party conference, which can easily hold its own with Donald Trump’s inaugural address a year earlier.

These findings confirm that we are living with a populist zeitgeist, in an era when aspects of populism have become dominant within the political debate. More and more mainstream politicians are using “pro-people” and/or “anti-elite” rhetoric to win voters – in part to fight off electoral challenges from true populist actors. But populist sentiments are not limited to party politics.

Both traditional and, particularly, social media are consumed by populist sentiment. Nowadays it is “common knowledge” (a popular populist phrase) that “the elite” is corrupt and that “common sense” (another one) is being ignored. Even movies and songs celebrate populist values, such as John Rich’s Shuttin’ Detroit Down (2009) and even Reese Witherspoon’s Sweet Home Alabama (2002). Programmes that celebrate “the people”, from American Idol to Big Brother have replaced those glorifying “the elite” – such as Lifestyles of the Rich and Famous.

This populist zeitgeist has also led to the normalisation of the term populism on both the left and the right by intellectuals and politicians. For instance, the rightwing Dutch premier, Mark Rutte, claims that (his) “good populism” is the best antidote to “bad populism”, even though the parties of “good populism” – Rutte’s conservative VVD and the (nominally) Christian democratic CDA – have nosedived in the polls; meanwhile “bad populism” is polling at record levels – ie Geert Wilders’ Party for Freedom (PVV) and Thierry Baudet’s Forum for Democracy (FvD).

And on the other side of the political spectrum, leftwing intellectuals such as Chantal Mouffe and politicians including Jean-Luc Mélenchon argue that only “left populism” can defeat the populist radical right.

Importantly, neither Rutte’s “good populism” nor Mouffe’s “left populism” is really populist in the sense that most scholars use the term today. As I have argued before, Rutte’s (good) populism is really nativism (lite). It attacks the ethnic other (notably Muslims) rather than the corrupt elite (of which his own party, the VVD – the People’s Party for Freedom and Democracy – is by far the most significant representative). And Mouffe’s “left populism” fundamentally rejects the monism that defines populism, instead defending a pluralist vision that, despite the rhetoric, is best described as social democracy.

In the public discourse, populism is mainly used as a synonym for anti-establishment sentiments, the idea that “the elite” is corrupt, or at least incompetent or ineffective. This sentiment is now so widespread that most “elites” – which include academics and journalists – have internalised it. With references to populist vagaries such as “common sense” and “silent majority”, they hope to show that they are on the side of “the people”, and therefore part of the political solution. In reality, they just confirm the frustrations and prejudices of the populist electorates.

The only way to change the populist zeitgeist is to denounce both populism (lite) and anti-populism – in which “the people” are seen as corrupt and the (former) elite as morally pure. As Mouffe rightly argues, we have to (re)politicise the political debate, but by openly acknowledging and respecting the pluralism of our societies – in terms of interests and opinions, rather than ethnicities or religions. This means that neither “the people” nor “the elite” should be essentialised and homogenised.

Hence, politicians have to stop pretending to speak for the people. Politics is, by definition, about a power struggle between different groups with a broad variety of interests and values. It is not the task of the politician to define what the people want, but to represent the interests of a specific subset of the people – that is, their electorate – while acknowledging the legitimate interests of other people and politicians. This means not just resisting the urge to copy populist rhetoric, but explicitly rejecting the foundations of populism.

• Cas Mudde is a Guardian US columnist