A showdown is shaping up in some of the nation's most conservative states over embryonic stem cell research, as opponents draw language and tactics from the battle over abortion to counter President Barack Obama's plan to ease research restrictions.

Legislation granting fertilized embryos "personhood" has gained momentum in at least three state legislatures. The strategy — which has been used to try to undermine the Roe v. Wade decision legalizing abortion — is now aimed at embryonic stem cell research. The scientific field uses stem cells from human embryos, which can develop into different kinds of adult cells, to seek answers about human health.

Opposition to both abortion and stem cell research hinges on the same issue: When does life begin? As a result, embryonic stem cell research has become the latest front in the decades-old battle over abortion.

"If you are someone who believes that a single cell embryo is a person then you are looking for any opportunity you can to make that argument. But as a country, legally, we've never accepted that," said Michael Werner of the Coalition for the Advancement of Medical Research. "The legislative tactics are the same."

Abortion opponents believe embryonic stem cell research is an assault on life in its earliest form. Fertilized embryos are destroyed when stem cells are extracted from them for research.

"No one's right for a cure supersedes someone else's right to life," said Dan Becker, president of Georgia Right to Life.

The opponents expect to push for restrictions in conservative-leaning states. And they say states must take the lead in pushing the abortion and stem cell issues into the increasingly conservative federal courts.

Legal experts said the state measures restricting stem cell research raise constitutional concerns in a largely untested area of law.

Alta Charo, professor of law and bioethics at the University of Wisconsin, said a new line of legal thought holds that scientific inquiry should be protected by the First Amendment, "like a political or religious statement or activity."

She said the measures restricting the use of fertilized embryos also raise questions about the right to procreation.

"The courts haven't settled this yet," Charo said.

While Louisiana already bans the destruction of fertilized embryos, the courts have not yet weighed in, Charo said.

In Georgia, a measure that would ban some forms of stem cell research on fertilized embryos is moving quickly through the state Senate. The bill would outlaw the destruction of fertilized embryos, which the legislation defines as a person. It is expected to face a vote in the full state Senate on Thursday.

Similar "personhood" measures have cleared one chamber each in Montana and North Dakota.

They come in the wake of a Colorado ballot initiative that said human life begins at conception. It failed to win voter approval last year.