Abstract: At points in American history, there have been significant, even massive shifts in constitutional understandings, doctrines, and practices. Apparently settled principles, and widely accepted approaches, are discarded as erroneous, even illegitimate, in favor of new principles and approaches. Less momentously, views that were once considered unthinkable do not quite become the law on the ground but instead come to be seen as plausible and part of the mainstream. Relatedly, Americans transform how they talk and think about their Constitution – its core commitments and underlying narratives – and those transformations change our practices. Our goal is to provide a conceptual map of radical constitutional change and to describe how and why such change occurs. First, we ask whether theories of interpretation trigger radical change or whether desires for radical change impel people to generate new (or modify old) theories of interpretation. Second, we explore why so many people are baffled or outraged by constitutional paradigm shifts. Third, we investigate the drivers of radical constitutional change, both the familiar bottom-up pressures from “We the People” and the less-familiar top-down approaches, where legal elites back and impose a new constitutional regime. Given that we might well be in the early innings of a radical constitutional change, it is an apt moment to theorize about the phenomenon writ large.