JOHNSTOWN, United States, Aug 31, 2024 (BSS/AFP) - Republican White House nominee Donald Trump sought Friday to contain the blast radius of a fierce backlash over his remarks publicly backing away from right-wing positions on reproductive rights.

The ex-president has been under fire from conservatives over an announcement that in a second term he would ensure free in vitro fertilization (IVF) -- an expensive fertility procedure that many in the anti-abortion movement want to see curbed.

The rift widened as he hit out at his home state Florida's six-week abortion ban, calling it too restrictive and suggesting he planned to vote for an upcoming ballot measure that would make the procedure legal until a fetus becomes viable.

Trump, 78, walked back the comment ahead of a rally in the battleground state of Pennsylvania on Friday, telling Fox News that "I will be voting no."

But conservatives had already begun criticizing Trump's ever-shifting positions on abortion, with a new Republican policy platform dropping calls for a national ban and the tycoon's recent claim that his government would be "great" for reproductive rights.

The pushback from anti-abortion groups on his latest remarks was swift, with activists warning that he risks alienating his base.

Evangelical theologian Albert Mohler said Trump's positions appeared "almost calculated to alienate pro-life voters" while conservative commentator Erick Erickson posted that Trump's abortion stance "will be a bridge too far for too many."

Trump's rally, in Johnstown, was notable for the absence of any remarks on reproductive rights, despite Thursday's big IVF announcement.

The campaign of Democratic candidate Kamala Harris was happy to weigh in on the issue, smelling blood in the water.

"The majority of Americans support abortion access, they support IVF, they support contraception," Mini Timmaraju, of the Reproductive Freedom for All lobby group, told reporters in a campaign call.

"(Trump) has finally figured it out, and he'll do anything to distract from his abysmal, horrifying record on this issue."

- 'He is pro-life' -

Trump has been all over the map on abortion in the last 15 years, initially describing himself as "pro-choice" before calling for "some form of punishment" for women seeking the procedure.

He boasts about appointing Supreme Court justices who ended federal protections for abortion access in 2022 but has more recently begun to worry that Republicans are out of step with the majority of voters on reproductive rights.

His IVF pledge appeared calculated to appeal to moderates but will upset conservatives who for years opposed Barack Obama's Affordable Care Act because they were against the redistributive economics of taxpayer-funded health insurance.

Almost every Senate Republican voted against assuring IVF access in a vote in June -- including Trump's running mate J.D. Vance -- and more than half of the House Republican lawmakers have sponsored legislation that threatens its legality.

Republicans are divided on fertility treatments such as IVF, with many hailing them as a boost to American families.

Others, with strong beliefs that life begins at conception, oppose IVF because the procedure can produce multiple embryos, not all of which get used.

Abortion rights activists worry that the Supreme Court decision threatens IVF and were given cause by a February ruling in Alabama that frozen embryos could be considered people, causing several clinics to briefly pause treatments.

Yet if the abortion and IVF rows threatened to alienate Trump's most loyal supporters, rally-goers in Johnstown weren't showing it.

"It's not enough to make me not vote for him, no way, because he is pro-life," said Lisa Davis, a 54-year-old retired office manager from the nearby town of Somerset.

"I know he wants to give some exceptions -- and I think there should be."

"Why should I pay with my tax dollars for a baby getting killed?" added retired nurse Rosemary Drzal, 69.

A fireside chat-style appearance at the conservative pressure group Moms for Liberty later Friday did not touch on the issue.