Secretary of State Scott Gessler announced Wednesday that backers of the personhood amendment fell about 3,900 signatures short of 86,000 needed to make November's ballot.
This is the first time supporters failed to get the proposal on the ballot on their first try.
They can still try again to collect more signatures in order to win a place on the ballot.
Similar measures were overwhelmingly defeated by Colorado voters in 2010 and 2008.
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