DENVER (AP) — A citizens’ campaign to undo a new Colorado law that would pledge the state’s presidential electoral votes to the national popular vote winner said it has easily surpassed the number of signatures required to put the law before voters next year.

If certified for the 2020 ballot, the referendum could mark the first time a state has joined what’s called the National Popular Vote Interstate Compact, only to have it challenged at the ballot box, backers and opponents say.

The compact would take effect if states with a collective 270 electoral votes — the number needed to win the presidency — agree to join. Including Colorado’s nine electoral votes, the 15 states and District of Columbia that now belong to the compact have a total of 196 votes.

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