Defining populism?

Does anybody have a coherent, usable definition of what counts as “populist”?

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If you tell me a politician or party is nationalist, illiberal, anti-immigration, anti-intellectual, socialist, anti-capitalist, fascist, liberal, conservative, etc., then you’ve imparted usable information that distinguishes them from other politicians or parties who aren’t those things. But what’s the defining feature that makes one politician or party “populist” and another not populist?

The closest sense seems to be that it’s a stylistic and rhetorical category for those who claim to speak on behalf of the majority against an establishment minority. But that’s the message literally every politician runs on (including incumbents!), and lots of supposedly populist positions aren’t actually shared by a majority of the electorate.

The term seems to obscure more than it illuminates, and it feels like journalists often reach for it as more neutral-sounding than a substantive ideological label. Its popularisation is driven by the false conflation of neutrality and objectivity, with the desire to be neutral depriving us of more objectively informative terminology.

Trump (to use the most common example) is a nationalist, a nativist, an authoritarian, a protectionist, an anti-intellectual, and debatably perhaps a conservative... but what makes him any more of a populist than were Obama or Bush or Clinton before him? What makes Le Pen a populist but Macron, a charismatic figure who smashed both establishment major parties in his rise to power, somehow not a populist?

We get a lot of think-pieces these days trying to define populism (usually but not exclusively the right-wing nationalist sort), but I’ve yet to see a definition that’s satisfying or can be consistently applied. It’s the category-label equivalent of trying to nail jello to the wall. Everybody and nobody is a populist, because the term doesn’t really mean anything.