Getting populism wrong can distort our understanding of political reality in at least two crucial ways. For one thing, there is the danger of equating populism — which justifiably has a bad name across Europe and in parts of the Americas — with legitimate protest against specific policies. At the same time, it underestimates the perils posed by actual populism, such as that of Trump and Marine Le Pen. Populists don’t just criticize elites or play on the prejudices of people using emotionally charged rhetoric. They posit that there is one true, unified people and that they alone are its legitimate representatives. In a pluralist democracy comprised of diverse interests and identities, this claim opens the path to excluding entire groups — and in the worst cases, to authoritarianism. Opponents of populism must be explicit about this danger: they should not pretend that the populist is just another type of politician, if a bit more emotional or uncouth. But they also have to avoid a trap: excluding the supporters of the excluders. This is the tactical error Hillary Clinton made when she criticized Trump voters as “deplorables.”Populism as a concept has been and is used loosely. Michael Kazin in The Populist Persuasion: An American History (1998) noted how the concept of "populism" in the 1980s and 1990s was at times watered down to the point of near-meaninglessness:
Populists always claim that they, and they alone, represent the people. Consider Trump’s salvific boast in his speech at the Republic National Convention: “I am your voice,” with the corollary: “I alone can fix it.” This rhetoric condemns other political contenders as entirely illegitimate. The populist does not just disagree about policy; disputes are always matters of character. Other politicians are corrupt, or they put elite institutions before the people. In a word, the defining orientation of the populist is not anti-elitist or even antiestablishment (for populists are perfectly content with the establishment when they are in power) but anti-pluralist. This attitude translates into exclusions both at the level of party politics — other politicians are crooked — and at the level of citizens: opponents are likened to traitors to the nation. [my emphasis]
Beginning in the mid-1980s, populism became something of a fashion statement. Journalists and copywriters affixed the term not just to campaigners and officeholders (a habit begun in the early 1970s) but also to talk-show hosts, cable networks, rock musicians, film directors, low-priced bookstores, even sports fans who boo when rich athletes play poorly. Hewlett-Packard, one of the largest corporations in America, advertised a new product as neither "liberal" nor "conservative" but "Populist ... the perfect printer for the masses"; while Banana Republic, a clothing outlet geared to young professionals, unveiled its "Men's 100% Cotton Twill POPULIST pants ... steeped in grass-roots sensibility and the simple good sense of solid workmanship ... No-nonsense pants for the individual in everyman."Ernesto Laclau did a great service in developing a systematic political theory to describe populism as a distinct political phenomenon in his book La razón populista [On Populist Reason] (2005). He notes that populism as a referent term "has always been ambiguous and vague in social analysis." But he approach populism as "a mode of constructing the political." And the frame of the populist construction is defining the People versus the Elite.
Defining what the common people want and then selling it to them has long been the forte of both merchandisers and politicians. Snapped a comedian in 1992, 'To be a populist, all you have to be is popular." Yet the promiscuous applications of the term conveyed something more compelling - the discrediting of alternatives.
The basic substantive flaw in Müller's argument is that all politicians in competitive elections are arguing in some form that they are a better representative for the people of that consistency than their opponent. That's not the same as calling all supporters of the opponent "traitors" or excluding all of them from being legitimately part of "the people," or denying them legitimate citizenship.
But he's not making a substantive argument so much as a polemic against the concept of populism, which he simply defines as "anti-pluralist." As he says in the quote above, "the defining orientation of the populist is not anti-elitist or even antiestablishment."
In other words, he defines populism as it actually exists in history and present-day politics, like in the Populist Party headed by William Jennings Bryan that gave the concept its name, as not being populist. Only those who brand their opponents as traitors who are not legimately part of the people or even citizens. For Müller, in other words only rightwing populism is populism. And therefore anything that pretends to be any other kind, like Bernie Sanders' Presidential campaign, is really just another form of rightwing populism. But despite his impressive scholarly credentials, his argument is so muddled that even the polemic is not terribly effective.
The argument that "populists are perfectly content with the establishment when they are in power" is ahistorical. It's actually just a play on words in which a government is by definition part of the "establishment." Populist governments can and do present themselves as defenders of the People against the Elite. Recent and current populist governments in Latin America, including those of the Kirchners and the Venezuelan regime, have represented themselves as defenders of the interests of the majority of the public (the People in the populist construction) against the economic elite. We can argue about whether their claims or legitimate or not. But it's a fact that populist governments can and do strike a posture as the defenders of the People against the Elite.
Admittedly, I'm saying that with an understanding of populism consistent with Laclau's history-based version.
The rest of the article is pretty much variations on that theme. For example, "Populism has no particular interest in getting people continuously to participate in politics." Except those who do. Again, the Kirchners in Argentina are an excellent example.
And, illustrating the confusion to which his approach leads, later in the article he refers to how in Latin Americas, "advocates of populism have always stressed its inclusionary and emancipatory character in what remains the economically most unequal continent on the globe." This he says of a type of movement that he defines as exclusionary.
Müller not only dismisses how populism constructs the concept of the elite. He essentially ignores the more vital element of constructing a People to oppose the elite, how that combination of a multi-class groups is put together and how a unifying symbolic representation of that groups is established. In fact, he manages to contort that whole process into arguing that constructing a popular alliance across class lines is a refutation of the claims of populists: "In some countries such as France and Austria, populist parties are effectively catchalls: they draw a large number of workers but also many from other walks of life."
Müller makes some more-or-less legitimate criticisms about making facile assumptions about the motivations of supporters of populist movements. But since he mangles the definition of populism, trying to apply those criticism to populism doesn't produce any particularly helpful analysis.