An insurgent antiabortion movement that is gaining momentum nationwide is hoping for its first electoral victory Tuesday, when Mississippi voters will decide whether to designate a fertilized egg as a person and potentially label its destruction an act of murder.

If approved, the nation’s first “personhood” amendment could criminalize abortion and limit in-vitro fertilization and some forms of birth control. It also would give a jolt of energy to a national movement that views mainstream antiabortion activists as timid and complacent.

“They’ve just taken an incremental approach,” said Les Riley, the founder of Personhood Mississippi and a self-described tractor salesman and father of 10 who initiated the state’s effort. “We’re just going to the heart of the matter, which is: Is this a person or not? God says it is, and science has confirmed it.”

“Life-at-conception” ballot initiatives in other parts of the country, including Colorado last year, have failed amid concerns about their far-reaching, and in some cases unforeseeable, implications.

But proponents of the amendment — who were inspired partly by the tea party movement — say they are more confident of victory in Mississippi, a Bible Belt state where antiabortion sentiment runs high and the laws governing the procedure are so strict that just one abortion clinic exists.

Opponents of the measure, including Planned Parenthood and the American Civil Liberties Union, have eroded support for it by casting it more broadly as an infringement on women’s health and an example of government overreach. Like backers of the amendment, dubbed “MS 26,” they have turned out at college football games to distribute literature and spent weekday evenings working phone banks — although not Wednesdays, because so many people attend church that day.

“A lot of people think this is just about abortion, but it’s not about abortion,” said Valencia Robinson, an abortion rights and HIV activist in Jackson, who spent Friday knocking on doors. “It’s bad for women’s health, it’s bad for our economy, and my strongest point is, it’s just government intrusion in our personal lives.”

Still, the Nov. 8 measure has broad support that stretches across party lines, with both the Republican and Democratic gubernatorial candidates voicing support for it (the Democrat, Johnny DuPree, has expressed concern about how it would affect birth control and in vitro fertilization).

For years, the strategy favored by conservative activists nationally has been to gradually decrease access to abortion by cutting government funding and imposing restrictions, such as requiring women to view ultrasound images before the procedure.

The aim has been to reduce the number of abortions while awaiting a mix of justices on the U.S. Supreme Court that would be inclined to overturn Roe vs. Wade, the 1973 decision that legalized abortion.

An energized group of activists has grown impatient with that approach. They take an uncompromising position on abortion, opposing it even in cases of rape and incest.

Some also oppose making exceptions to save the life of the mother, arguing that both lives are equal and that doctors do not have the right to choose to save one over the other. Some even object to the term “fertilized egg.”

“It’s an embryo,” said Walter Hoye, a California pastor and president of the Issues 4 Life Foundation. “Calling it a fertilized egg is dehumanizing.”

Personhood efforts are under way in more than a dozen states, including Alabama, Arkansas, Georgia and Ohio. The movement has grown recently with the help of passionate young antiabortion advocates and more seasoned activists who have grown disenchanted with the pace of change.

They view their approach as an answer to the Roe decision, which concluded that the term “person” does not apply to the unborn under the 14th Amendment. “If this suggestion of personhood is established,” Justice Harry Blackmun wrote in the opinion, the abortion rights advocate’s case “collapses, for the fetus’ right to life would then be guaranteed specifically by the Amendment.”

“I see that as a directive from the court that says, look, if you want to protect unborn children, you’d better recognize them as persons in the full legal sense,” said Rebecca Kiessling, spokeswoman for Personhood USA. Kiessling, a lawyer, is the product of rape; her mother tried twice to obtain back-alley abortions before giving her daughter up for adoption, Kiessling said.

Many legal experts say the activists are misinterpreting Blackmun’s language, and that the Mississippi measure likely would not stand up in court.