The Constitution, then, spells out four paths for an amendment:
* Proposal by convention of states, ratification by state conventions (never used)
* Proposal by convention of states, ratification by state legislatures (never used)
* Proposal by Congress, ratification by state conventions (used once)
* Proposal by Congress, ratification by state legislatures (used all other times)
http://www.usconstitution.net/constam.htmlArticle V - Amendment Note1 - Note2 - Note3
The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress; Provided that no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses in the Ninth Section of the first Article; and that no State, without its Consent, shall be deprived of its equal Suffrage in the Senate.
Amendment 27 - Limiting Congressional Pay Increases
No law, varying the compensation for the services of the Senators and Representatives, shall take effect, until an election of Representatives shall have intervened.
27th Amendment
The 27th Amendment was originally proposed on September 25, 1789, as an article in the original Bill of Rights. It did not pass the required number of states with the articles we now know as the first ten amendments. It sat, unratified and with no expiration date, in constitutional limbo, for more than 80 years when Ohio ratified it to protest a congressional pay hike; no other states followed Ohio's lead, however. Again it languished, for more than 100 years.
In 1978, Wyoming ratified the amendment, but there was again, no follow-up by the remaining states. Then, in the early 1980's, Gregory Watson, an aide to a Texas legislator, took up the proposed amendment's cause. From 1983 to 1992, the requisite number of states ratified the amendment, and it was declared ratified on May 7, 1992 (74,003 days).
http://www.usconstitution.net/xconst_Am27.html