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Michael Conroy, Associated Press
In this June 12, 2014, file photo, Indiana Senate President Pro Tempore David Long welcomes delegates meeting to set up the framework for states to amend the U.S. Constitution, at the Statehouse in Indianapolis. As Republicans win control of more legislatures across the country, some want to use their growing state power to limit federal spending, and are considering a national constitutional convention, an idea that hasn’t been used since George Washington’s.

AUSTIN, Texas — As Republicans win control of more state legislatures, some want to use their growing power to limit federal spending — and are considering an idea that hasn't been used since George Washington's day.

Their plan: Persuade the states to call a national constitutional convention to add a balanced budget amendment to the Constitution.

Calling a constitutional convention requires a vote of 34 states. The GOP now controls both legislative chambers in 30.

Convention proposals were introduced or discussed in about three dozen legislatures this year and approved by three.

Unlike other parts of the conservative agenda that have sailed through GOP statehouses, the convention debate is complicated because it involves three separate proposals.

And even some leading Republicans consider a possible convention too unpredictable or dismiss the concept as farfetched.