"To get the initiative on the 2018 ballot, the coalition must collect at least 98,492 signatures from registered voters — or 5 percent of the votes cast in the most recent secretary of state election. Voters can approve ballot initiatives with a simple majority. For constitutional measures, the signature and vote thresholds are significantly higher."

Broader, perhaps, but not higher for signatures. 3.7M voters in CO, so 74K Signatures for amendments vs 98K for ballot initiatives.