Despite a clerical error that moved up the deadline by three days, volunteers with Personhood Colorado say they collected nearly 4,000 more signatures than the 76,000 needed by Friday's deadline.
The proposal would change the definition of humans in the state constitution to include fertilized embryos.
A similar ballot issue failed in 2008.
The Colorado Secretary of State's office still needs to certify the signatures.
(KUSA-TV © 2010 Multimedia Holdings Corporation)