The recent electoral success of leftwing populist parties such as Syriza in Greece and Podemos in Spain has given a new impulse to the debate on populism in Europe. Until now, populism was almost exclusively linked to the radical right, leading to an incorrect conflation of populism and xenophobia. In its original form, populism is an ideology that considers society to be ultimately separated into two homogenous and antagonistic groups: “the pure people” and “the corrupt elite”, and argues that politics should be an expression of the volonté générale (general will) of the people. Practically, populist politicians almost always combine it with other ideologies, such as nativism on the right and socialism on the left.

Up until a couple of years ago the consensus among European elites on the left and right was that populism was inherently bad. It was dismissed as a “pathology of democracy” or, as the American historian Richard Hofstadter wrote in the 1960s, “the paranoid style of politics”. The rise of leftwing populist movements and parties has seen a shift in the public debate, particularly pushed by followers of Chantal Mouffe and the late Ernesto Laclau, who argue that populism actually constitutes the essence of democratic politics. In their view populism is good for democracy; it is liberalism that is the real problem. Simply stated, both are right and wrong. The relationship between populism and liberal democracy is complex and includes the good, the bad and the ugly.

The main good is that populism brings to the fore issues that large parts of the population care about, but that the political elites want to avoid discussing; think about immigration for the populist right or austerity for the populist left. Leaders from different parties can come together to keep issues that divide their respective electorates off the agenda – such as European integration and immigration.

In other cases they take it even a step further, excluding controversial areas from the democratic process altogether by putting independent, technocratic institutions in charge (such as the courts or central banks). In many cases political elites have worked hand in glove with cultural and economic elites, leaving virtually no space for democratic opposition. To paraphrase the Mexican political theorist Benjamin Arditi, in those cases populism behaves like the drunken guest at a dinner party, who doesn’t respect the rules of public contestation but spells out the painful but real problems of society.

The main bad is that populism is a monist and moralist ideology, which denies the existence of divisions of interests and opinions within “the people” and rejects the legitimacy of political opponents. As the populists are the vox populi, ie the voice of all the people, anyone with a different view speaks for “special interests”, ie the elite. Given that the key distinction is between the pure people and the corrupt elite, any compromise would lead to the corruption of the people and is therefore rejected. This uncompromising stand leads to a polarised political culture, in which non-populists turn into anti-populists.

Populism tends to get ugly when it gets into power. If it has to share power with non-populists the effects, positive or negative, tend to be small (think about the Schüssel governments with the populist, radical right FPO in Austria). Even when populists dominate the government, as is now the case in Greece, the negative aspects of populism often are limited, although not for a lack of trying. Populists like Silvio Berlusconi in Italy, the Kaczyńskis in Poland, or Vladimír Mečiar in Slovakia regularly tried to circumvent or undermine the power of countervailing forces, including independent judges and the political opposition. In most cases they were successfully opposed by other parts of the political structure – often with help from outside influences, most notably the European Union.

However, the current situation in Hungary and Venezuela shows us what populism can do when it takes full control of a country. Supported by impressive popular majorities in elections, populist leaders like Viktor Orbán and Hugo Chávez have introduced new constitutions that significantly undermine the checks and balances of liberal democracy. In addition, loyalists have been put at the head of non-majoritarian institutions, such as the courts and other oversight committees, often for periods that extend well beyond the legislative term. Any opposition is frustrated by a combination of legal and extra-legal pressures, from raids by tax agencies to the rejection of renewals of media licences.

In short, populism is an illiberal democratic response to undemocratic liberalism. It criticises the exclusion of important issues from the political agenda by the elites and calls for their repoliticisation. However, this comes at a price. Populism’s black and white views and uncompromising stand leads to a polarised society – for which, of course, both sides share responsibility – and its majoritarian extremism denies legitimacy to opponents’ views and weakens the rights of minorities. While leftwing populism is often less exclusionary than rightwing populism, the main difference between them is not whether they exclude, but whom they exclude, which is largely determined by their accompanying ideology (eg nationalism or socialism).