Donald Trump this week proposed subsidizing in-vitro fertilization treatments for all Americans, and the politics aren’t hard to discern. Mr. Trump is trying to blunt a GOP liability with women voters, particularly on abortion. But a new federal fertility entitlement is a fiscal and cultural thicket Republicans don’t want to enter.

“I’m announcing today in a major statement that under the Trump Administration your government will pay for—or your insurance company will be mandated to pay for—all costs associated with IVF treatment,” Mr. Trump said at a campaign stop on Thursday. He didn’t offer details, but his announcement proves again that elections are dangerous for taxpayers.

Most Americans know someone who has struggled to conceive children, and couples often turn to IVF procedures that cost tens of thousands of dollars from egg retrievals to embryo transfers. Insurers don’t always cover IVF, though companies appear to be expanding fertility benefits as more Americans form families at later ages. In 2022 some 43% of large employers covered IVF, up from 27% in 2020, according to one survey.

The irony is that Mr. Trump is mimicking Barack Obama and his Affordable Care Act, which demanded that insurers offer the federal government’s preferred benefits regardless of expense. The cost of fertility procedures for some will be buried across higher premiums for everyone else. If Mr. Trump forces Affordable Care Act plans to cover IVF, he will encourage more Americans to move to taxpayer subsidized plans from small business offerings that often can’t afford to cover IVF.

The cost could run into the tens of billions annually, not least if Medicaid had to cover IVF, which it inevitably will if ObamaCare plans do. The government would dictate how many attempts are covered when an IVF cycle fails, and micromanage the quality of clinics. If you think IVF is expensive now, wait until it’s “free.”

And those are the easy issues. The creation of embryos implicates profound questions of human life, and even some Americans who support the availability of IVF appear to have misgivings or nuanced views. Some 82% of Americans called IVF “morally acceptable” in a Gallup poll this summer, but only 49% similarly approved of the destruction of leftover embryos created in the process.

Remember when the Little Sisters of the Poor had to fight Mr. Obama in court to vindicate their right not to cover birth control options they viewed as abortifacients? Mr. Trump’s IVF mandate would similarly risk commanding the money and consciences of those who object. America’s cultural divides are inflamed enough without an extended federal debate about fertility practices.

Mr. Trump also floated allowing parents to deduct newborn expenses on their taxes, which underscores his political and fiscal profligacy. He isn’t thinking about the policy consequences, only about winning a campaign bidding war with Democrats. Kamala Harris is promising a $6,000 tax credit for newborns.

Mr. Trump still fancies himself a political outsider, but nothing is more predictable than a politician promising some new handout to stop his slide in the polls. The IVF entitlement is a half-baked proposal from a Republican Party increasingly confused about its economic and cultural principles.

This editorial was published Aug. 31 by The Wall Street Journal.