Political polarization and extremism are on the rise in the United States. Many seek to understand this trend by comparing the extreme left and right, obviating a deep understanding of the left. Here, we differentiate Leftists from Liberals in terms of identity, ideology, morality, and political preferences. We used both quantitative and qualitative methods to compare Leftists and Liberals we recruited from online political spaces and Prolific (N = 517). Rather than identifying as more extreme Liberals, Leftists see themselves as a distinct group, defined by their anti-capitalist ideology, and desire for radical societal change. This is part of a general moral opposition to the status quo, which negatively predicts support for Joe Biden, by Leftists but not Liberals, right before the 2020 election. In sum, Leftists are a distinct and meaningful identity group, whose ideology can help us understand radicalism and its links to political division more broadly.