To answer my [narrower] question (and in relation to the answer on the Lumpenproletariat), Marxism-Leninism posited a special role for the Party in illuminating and leading the proletariat. It is thus not exactly a pure populist approach if we concede that the Party was basically an elite. As elaborated in a paper,
Among the most famous left-wing populists were the Russian Narodniki of the 19th century. Their ideas informed Lenin’s and therefore Marxism-Leninism as a whole, especially its radical rejection of constitutional limits on the state and its assertion of the revolutionary potential of the peasantry. [...] The Communist Party of the Soviet Union’s declaration in the 1960s that it was a ‘party of the Soviet people’ appeared to indicate that populism had become mainstream.
However, this argument can be overstated: Marxism-Leninism’s concern with doctrinal purity and correct class politics only evaporated under Gorbachev, while the emphasis on the elite party of dedicated revolutionaries and communist socialization is inherently anti-populist. Populists do not aim to educate or change their chosen people, and argue that “the consciousness of the people, generally referred to as common sense, is the basis of all good [politics].” [quoting Mudde] For the Marxist-Leninist, the Party is the epicenter of politics: it leads and guides popular interests, rather than simply reflecting them, hence the often anti-populist communist campaigns of the Soviet Union such as Gorbachev’s 1985–86 anti-alcohol campaign that sought to instill labor discipline among the Soviet people.
It's also interesting to note here that Laclau described himself as a "post-Marxist" and he rejected "kindergarten" Leninism.