Even two of the state’s largest anti-abortion groups have stopped short of endorsing House Bill 1500 because of its glaring constitutional problems.

In a legislative session so far characterized by a focus on school finance and property tax cuts, growing support for a controversial abortion bill is threatening to disrupt the relative harmony among lawmakers.

Fifty-six House Republicans have signed onto a bill by state Representative Briscoe Cain, R-Deer Park, that refers to a fetus as an “unborn child” and would outlaw abortion as early as six weeks, before most women even know they are pregnant. Critics say the so-called fetal heartbeat bill amounts to an effective ban on the constitutionally protected medical procedure. Similar legislation has been filed in more than a dozen other states, and laws passed in Iowa, North Dakota and Arkansas have been struck down as unconstitutional.

Even two of the state’s largest anti-abortion groups have stopped short of endorsing House Bill 1500 because of its glaring constitutional problems. Still, far-right Republicans are pushing ahead, emboldened by an ever-zealous base, a new conservative majority on the U.S. Supreme Court and a like-minded president.

It wouldn’t be the first time the GOP-dominated Legislature passed legislation that was ultimately found unconstitutional — but abortion-rights activists worry damage could be done before a court steps in.

Former state Senator Wendy Davis called the bill “the most dangerous I’ve ever seen” in a call to action last week. Davis, whose filibuster of a suite of anti-abortion legislation in 2013 fueled a political movement, said her nonprofit Deeds Not Words is planning to launch a statewide petition opposing the measure. Current state law bans abortion after 20 weeks.

Only three of the bill’s 56 joint or co-authors are women: GOP state Representatives Valoree Swanson, who walked away when asked about her support at the Capitol; Candy Noble, who declined to comment; and Stephanie Klick, who did not respond to a request for an interview.

Asked about the dearth of female lawmakers supporting the bill, state Representative Jonathan Stickland, a Bedford Republican who is a co-author, pointed to the drop in GOP women in the House — this session, the number has fallen to six — and said, “I can’t speak for them. For those of us that support it, I think we’re trying to protect women, especially the unborn.”

Aimee Arrambide, executive director of NARAL Pro-Choice Texas, agreed with Davis that the measure is one of the most dangerous challenges to abortion access.

“We saw anti-abortion politicians quiet on the campaign trail in regards to restricting abortion access and focusing on the kitchen-table issues Texans care about because they were concerned with re-election,” Arrambide said in an email. “Now that the Legislature is in session, anti-abortion politicians are ignoring a diverse Texas electorate that overwhelmingly supports abortion access and instead pandering to special interest groups.”

Cain, who calls his bill “common sense,” said he’s encouraged by the overall number of co-authors. “[It] shows that it’s important to Texas.”

State Representative Lina Ortega, D-El Paso, said she doesn’t believe the bill, which has not yet been referred to a committee, will make it to a full floor vote.

“Even though there’s sometimes a clear divide between Democrats and Republicans on those types of bills, I don’t believe that there would be enough moderate Republicans that would support a bill like that,” Ortega said. She pointed out that three of six Republican women in the House haven’t signed onto the bill.

Across the country, 2019 has seen the greatest number of states — at least 10, including Texas — propose “fetal heartbeat” bills, and the governors of Florida and Ohio have pledged to sign them into law. So far, Texas Governor Greg Abbott has been silent on the proposal.

“Anti-abortion politicians are ignoring a diverse Texas electorate that overwhelmingly supports abortion access and instead pandering to special interest groups.”

The Texas bill uses questionable medical claims and language identical to legislation in other states. That includes a definition of “gestational age” that suggests that conception begins on the first day of the woman’s last menstrual period — even though doctors (and religious doctrines) do not agree on when pregnancy begins. Also included in Cain’s measure is a false claim that fewer than 5 percent of pregnancies end in miscarriage after the detection of a fetal heartbeat, incorrectly implying that a heartbeat is a guarantee of a fetus’ viability.

“It helps change hearts and minds when you realize that this unborn child has a heartbeat,” Cain said.

But anti-abortion groups Texas Alliance for Life and the more hardline Texas Right to Life aren’t throwing their full support behind HB 1500. Joe Pojman, director of Texas Alliance for Life, said while he’s excited about the number of lawmakers signing on, his group is not recommending that the Legislature pass it. “We’re just recommending bills that have a reasonable chance of sustaining a federal court challenge,” Pojman said.

Elizabeth Graham, director of Texas Right to Life, did not directly answer the Observer’s questions about whether she supports the proposal, saying only that Texas Right to Life aims to challenge Roe v. Wade through “incrementally prudent steps.”

“The legislative team and I are closely monitoring the heartbeat bill and analyzing how that fits into our long-term strategy of challenging Roe,” Graham said in an email.