Since then, women’s advocates have repeatedly tried to get Congress to adopt a new ERA resolution and begin ratification anew—to no avail.

But advocates also formulated a new path to ratification, which they dubbed the “three-state strategy.” It is this: (1) Win ratification in three of the 15 states that have not yet ratified the amendment—thus bringing the total number of ratifications to 38, and then (2) Win passage of a congressional resolution retroactively extending the deadline.

Step one is nearly complete; the Nevada legislature approved the amendment in 2017, and Illinois did so in 2018. If Virginia approves it this time, the three-state strategists will ask Congress to pass a statute proclaiming that the measure has been approved by 38 states.

Then the real fight will start.

The “new” strategy is actually 25 years old. It has its roots in 1992, after the adoption of the Twenty-Seventh Amendment.

Quick! What is the Twenty-Seventh Amendment? Don’t worry, nobody remembers: “No law, varying the compensation for the services of the Senators and Representatives, shall take effect, until an election of representatives shall have intervened.” It means that one Congress can’t vote itself a pay raise; it can only raise (or lower) the pay of the next Congress, thus requiring the members to face voters at the polls before pocketing extra cash.

Although this congressional-pay amendment entered the Constitution in 1992, it had actually been proposed by Congress two centuries earlier, in 1789. It passed through both chambers and went to the states. There it disappeared, ratified by only six legislatures.

Read: How the U.S. Congress keeps getting paid to do nothing

Flash forward to 1982, when a University of Texas undergraduate named Gregory Watson wrote a term paper suggesting that citizens could still push the pay amendment to ratification. His instructor gave him a C, but Watson devoted himself to the project for the next decade, until on May 9, 1992, Michigan became the 39th state to sign on.

Final ratification took place amid a national outcry against Congress after a (by today’s standards) very mild scandal involving generous check-cashing privileges at a bank for members of Congress. Public opinion was such that no member had the nerve to obstruct it. So on May 18, 1992, the archivist of the United States certified the amendment as part of the Constitution, and both chambers later affirmed his decision.

Note that Article V of the Constitution doesn’t even mention time limits, and they didn’t come into use until the 20th century. In 1921, the Supreme Court held that Congress could put such limits into a proposed amendment—but not that it is required to do so. Of 20th-century amendments, the Eighteenth, Twentieth, Twenty-First, and Twenty-Second Amendments included limits in the text of the proposed amendment. The Sixteenth, Seventeenth, Nineteenth, and Twenty-Third Amendments included no time limit at all. And the drafters of the ERA, by design or luck, did not put the seven-year time limit into the text of the proposed amendment itself—instead, as in three other 20th-century amendments, it is in the resolution language proposing the text.