How does the amendment process work?

The amendment process works by requiring an amendment to be proposed and then ratified through the procedure set out in Article V of the Constitution, with both stages requiring substantial supermajorities. There are two routes for proposal and two for ratification. Proposal requires either a two-thirds vote of both the Senate and the House of Representatives, or a constitutional convention called by Congress at the application of two-thirds of state legislatures, currently 34 of 50 states. The convention route has never been successfully used, although applications have been filed for various proposed amendments.

Ratification requires approval by three-fourths of the states, currently 38 of 50, either through their legislatures or through state conventions specially convened for the purpose. Congress chooses which ratification method applies. Only the Twenty-First Amendment, which repealed Prohibition in 1933, has been ratified by state conventions; the other 26 went through state legislatures.

The Founders set the bar deliberately high. James Madison, the principal architect of Article V, explained at the Convention and in Federalist No. 43 that the process was meant to guard equally against that extreme facility, which would render the Constitution too mutable; and that extreme difficulty, which might perpetuate its discovered faults. The supermajority requirements force broad regional, partisan, and ideological consensus before the basic rules of government change.

The process is slow. The Twenty-Seventh Amendment, which delays congressional pay raises until after the next House election, was first proposed by James Madison in 1789 and not ratified until 1992, more than 200 years later. The Equal Rights Amendment, proposed in 1923 and approved by Congress in 1972, fell three states short of ratification by its 1982 deadline. Some amendments have been ratified within months, especially the Bill of Rights in 1791, the Twenty-Sixth Amendment lowering the voting age in 1971 ratified in just over three months, and the Twenty-Fifth Amendment on presidential succession in 1967.

Once thirty-eight states ratify, the amendment becomes part of the Constitution with the same force as the original text and overrides any conflicting earlier provision. Ratifications cannot be rescinded once given, although the legal status of state rescissions has occasionally been disputed.