A growing number of Republican-led states are moving forward with efforts to make it more difficult for citizen-led ballot initiatives to succeed.

The latest move has come in Missouri , where the GOP-controlled Legislature gave final approval Friday to a bill that would significantly raise the threshold to amend the state constitution through that process. The legislation, once signed by the governor, will still need to be approved by voters.

So far this year, lawmakers have advanced or enacted bills that would create more hurdles for the citizen-led ballot measure process in at least seven other states, according to an NBC News review, including Arkansas, Florida and Oklahoma.

And the Fairness Project , a nonprofit organization that helps progressive groups advance ballot measure

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