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An anti-abortion group in Ohio is facing a significant shortfall in the number of signatures needed to ask voters in the presidential battleground this fall whether the state constitution should declare that life begins when a human egg is fertilized, throwing up another obstacle for the "personhood" movement.

With less than two weeks before a crucial July deadline, the group's director says it has close to 20,000, or 5 percent, of the roughly 385,000 signatures required for the proposed personhood constitutional amendment to appear on November ballots.

Stacks of signatures have yet to be counted, and more arrive each day.

Still, Patrick Johnston, the director of Personhood Ohio, acknowledges that the group might not get enough signatures in time to make the ballot for this year's presidential election.

"I don't know what I'm going to get the last week of this month, but it needs to be a ton to get it by July 4," Johnston said in an interview this week with The Associated Press.

The personhood movement has already faced setbacks in other states this year. Supporters fell short of the required number of signatures to qualify for the November ballots in Nevada and California. And in Oklahoma, the state's highest court halted an amendment effort there to grant personhood rights to human embryos, saying the measure is unconstitutional.

Voters have rejected similar proposals that made ballots in 2008 and 2010 in Colorado. They also defeated the initiative last November in Mississippi, which has some of the nation's toughest abortion regulations.

Organizers say personhood amendments have a good chance to qualify for fall ballots in Montana and again in Colorado. Each state has a lower threshold of required signatures than Ohio. About 86,000 signatures are needed by early August in Colorado, while fewer than 49,000 are required by Friday in Montana.

The measures vary in some details, but in general they define human life as beginning with fertilization and are intended to ban virtually all abortions, even in cases of rape and incest. Many physicians have said the measures could make some birth control illegal and deter in vitro fertilization.

Supporters in Ohio have hoped to alleviate those concerns by rephrasing their proposed amendment to say it wouldn't affect "genuine contraception" or in vitro fertilization procedures.

Backers of the state constitutional amendments hope to spark a legal challenge to the landmark Roe v. Wade decision by the U.S. Supreme Court in 1973 that gave women a legal right to abortion.

The proposal hasn't attracted support from some traditional supporters of Ohio's anti-abortion measures.

The anti-abortion group Ohio Right to Life is not involved. And while it hasn't taken a formal position, the Catholic Conference of Ohio is not encouraging its 785 parishes to gather signatures.

Mike Gonidakis, Ohio Right to Life's president, said the organization believes the best way to overturn Roe v. Wade is by electing an anti-abortion president who will appoint sympathetic Supreme Court justices. Pointing to the amendment's previous defeats in Colorado and Mississippi, he said, "we would lose ... It would be really difficult to compete with the Hollywood money that would come into Ohio."

Other conservative groups that support the personhood amendment say they don't have the time or money to spend on it.

"We have to choose our battles," said Phil Burress, president of Citizens for Community Values. "And this year, our battle is getting our people to the polls."

The amendment is also trying to gain traction at the same time as the so-called heartbeat bill, which would outlaw abortions at the first detectable fetal heartbeat, sometimes as early as six weeks into pregnancy.

Denver-based Personhood USA is helping state personhood campaigns. It's spent money on mailings and robocalls in Ohio, but the group doesn't plan to hire paid circulators to help gather signatures in the final weeks, said Keith Mason, the organization's president. Instead, the Ohio amendment's fate will hinge on what volunteers collect.

Activists from across the political spectrum say getting an issue on Ohio's ballots is a daunting task.

The We Are Ohio campaign, which successfully sought the 2011 repeal of the state's collective bargaining law, hired paid signature gathers even with the support of well-funded labor unions, the Ohio Democratic Party and thousands of volunteers.

Dennis Willard, communications director for We Are Ohio, described the paid circulators as "a guaranteed backup plan."

Burress, who headed the campaign that successfully promoted passage of the state's 2004 amendment to ban gay marriage, said the personhood group is going to need close to 500,000 signatures ensure they have enough.

"Unless a miracle occurs, they are probably going to be looking at 2013," Burress said.

Johnston said Personhood Ohio volunteers will push hard in the final days to circulate petitions in churches on Sundays and sign people up at conferences, fairs and festivals.

"I pray we make it," Johnston said.

And if they don't? "We're going to keep working until we get the signatures and see that everyone's child is protected by love and by law," he said.