Denver, CO (LifeNews.com) -- Colorado abortion advocates staged a rally on Tuesday against a potential ballot proposal to amend the state constitution to define unborn children as persons under state law. The measure could set off a statewide battle over abortion, embryonic stem cell research and other practices that kill people before birth.

The pro-life group Colorado for Equal Rights has to submit 76,000 signatures by May 13 to qualify the measure for the ballot.

However, abortion advocates aren't waiting for the ballot battle to become official before condemning the proposal.

Members of the newly-formed pro-abortion group Protect Families, Protect Choices rallied on the capitol steps and claimed the measure would violate women's right to basic health care.