Historically, academic definitions of populism vary, and people have often used the term in loose and inconsistent ways to reference appeals to "the people",
"catch-all" politics. The term has also been used as a label for new parties whose classifications are unclear. Unlike word-order draws out vagueness abt who and how c-es & s-es differ from and what they call themselves}} conservatives or socialists, populists rarely call themselves "populists" and usually reject the term when it is applied to them, which throws some doubt on the usefulness of the term "populist".
In recent years, academic scholars have produced definitions that facilitate populist identification and comparison. Daniele Albertazzi and Duncan McDonnell define populism as an ideology that "pits a virtuous and homogeneous people against a set of elites and dangerous 'others' who are together depicted as depriving (or attempting to deprive) the sovereign people of their rights, values, prosperity, identity, and voice".
 Rather than viewing populism in terms of specific social bases, economic programs, issues, or electorates as discussions of right-wing populism have tended to do,
 this type of definition is in line with the approaches of scholars such as
Yves Meny and
 who have all sought to focus on populism per se, rather than treating it simply as an appendage of other ideologies.
In the United States and Latin America, populism has generally been associated with the left, whereas in European countries, populism is more associated with the right. In both, the central tenet of populism—that democracy should reflect the pure and undiluted will of the people—means it can sit easily with ideologies of both
left. However, while leaders of populist movements in recent decades have claimed to be on either the left or the right of the
political spectrum, there are also many populists who reject such classifications and claim not to be "left wing", "
centrist" or "right wing".
Some scholars argue that populist organizing for empowerment represents the return of older "Aristotelian" politics of horizontal interactions among equals who are different, for the sake of public problem solving.
 Populism has taken left-wing, right-wing and even centrist forms
 as well as forms of politics that bring together groups and individuals of diverse
 In 1912, Governor
John Shafroth and the Colorado legislature in a special session created the unique
Colorado Caucus to reform the domination of big business in that state. The use of populist rhetoric in the United States has recently included references such as "the powerful
trial lawyer lobby",
liberal elite", or "the
 Examples of populist rhetoric on the other side of the political spectrum include the anti-corporate-greed views of the
Occupy Wall Street movement and the theme of "
Two Americas" in the 2004 Presidential Democratic Party campaign of
Populists are seen by some politicians as a largely
democratic and positive force in society, while a wing of scholarship in political science contends that populist mass movements are irrational and introduce instability into the political process.
Margaret Canovan argues that both these polar views are faulty and has defined two main branches of modern populism worldwide—agrarian and political—and mapped out seven disparate sub-categories:
- Commodity farmer movements with radical economic agendas such as the American
People's Party of the late 19th century.
- Subsistence peasant movements, such as the
Eastern European Green Rising militias, which followed World War I.
- Intellectuals who romanticize hard-working farmers and peasants and build radical
agrarian movements like the Russian
- Populist democracy, including calls for more political participation through reforms such as the use of popular referenda.
- Politicians' populism marked by non-ideological appeals for "the people" to build a unified coalition.
Reactionary populism, such as the white backlash harvested by
- Populist dictatorship, such as that established by
Getúlio Vargas in Brazil.