It’s only a short phrase buried in the U.S. Constitution, but it enables an unprecedented avenue to change the law of the land: If two-thirds of the states demand it, Congress “shall call a convention” for proposing constitutional amendments.
A hopeless pipe dream? Actually, no; the issue is front and center right now. Some 27 states have active calls for a convention on a balanced budget amendment, which would force the federal government to pass budgets that do not enlarge the national debt. This means that theoretically just seven more have to act for a constitutional convention to be called, at least on that subject.