HELENA, Montana — The Montana Senate on Tuesday endorsed a measure that would ask voters to change the state constitution to define life as beginning at conception, an effort to ban abortions.

The bill passed the House 66-33 on a party-line vote last month. Since it seeks to amend the constitution, it needs 34 votes in the Senate to reach a two-thirds majority of the Legislature. The Senate endorsed the bill 30-20 on second reading Tuesday and it will receive a third-reading vote. However, there are 31 Republicans in the Senate, not enough to reach the needed margin.

The Montana Constitution states that no person shall be deprived of life, liberty or property without due process of law. The bill would change the constitution to define person as “all members of mankind at any stage of development, beginning at the stage of fertilization or conception, regardless of age, health, level of functioning or condition of dependency.”

The bill is the latest of several measures advanced in the GOP-controlled state to limit abortion access after voters elected the state’s first Republican governor in 16 years.

Democratic Sen. Jen Gross of Billings said voters have rejected efforts to put the issue on the ballot and that similar legislation has failed year after year.

“This is an attempt to build up a legal basis to ban abortion as quickly as possible if and when Roe (v. Wade) should be overturned,” she said.

Democratic Sen. Diane Sands of Missoula said such a constitutional amendment would ban some forms of birth control, emergency contraception — even in the case of rape or incest — and establish a constitutional basis for prohibiting in vitro fertilization. She said Montana’s Constitution protects a fundamental right to privacy in making medical decisions.

“You can pass a law, but you’re not going to stop it,” Sands said.

Republican Sen. Greg Hertz of Polson urged support of the bill, saying Montana already has a law that allows someone to be charged with homicide if a person knowingly causes the death of the fetus of another with knowledge that the woman is pregnant.

Republican Sen. Tom McGilvray of Billings said the bill is about looking out for human beings.

“This is about civility, this is about decency and this is about humanity,” he said. “And I would just urge us to go with our gut, go with our instinct. We know that that baby is a person. Let’s give the people of Montana a chance to weigh in on this.”

The Legislature has already passed bills to ban abortions after the unborn child is 20 weeks old; one that would require a pregnant woman be given the chance to view an ultrasound and listen to the fetal heart tone of an unborn child before undergoing an abortion and one that would require medicine-inducted abortions be provided in person by a medical practitioner.

The bills have not yet been forwarded to Gov. Greg Gianforte for his signature.