Bruce Ackerman's theory of "constitutional moments": the US Constitution changes not only through formal amendment but through transformative periods of popular mobilization that are later ratified by the courts.
His examples: Reconstruction (13th-15th Amendments and their interpretation), the New Deal (the "switch in time that saved nine"), the civil rights era. In each case, a political movement achieved changes that formal amendment couldn't or didn't accomplish.
The implication: constitutional law is not purely legal but also political. The formal text underdetermines outcomes; politics fills the gap — but not transparently.