Before former President Obama left office, he made a last-ditch effort to protect Planned Parenthood’s state funding from conservative governors and state legislatures that might seek to take it away.

But on Thursday, Vice President Mike Pence cast the tie-breaking vote in the Senate to send a bill to President Trump’s desk that would block that effort. The bill makes use of an obscure law called the Congressional Review Act, which lets Congress fast-track a resolution to disapprove of new federal agency rules within 60 days of their passage.

The rule, which Obama signed in December, would prohibit discriminating against family planning providers for reasons other than the quality of care they offer.

To be clear, this vote wasn’t about the big federal “defund Planned Parenthood” bill that Republicans have promised to pass at the same time as they repeal the Affordable Care Act. That proposal, which went down along with the failed Republican effort to repeal and replace the Affordable Care Act, would block Planned Parenthood from accepting hundreds of millions of dollars in federal Medicaid reimbursements.

This action is less sweeping, but it also affects more than just Planned Parenthood. It deals with how states can spend federal grant money on other low-income family planning providers, too. Rather than eliminating all federal Planned Parenthood funding nationwide, this is more about giving states the option to deny public funds to Planned Parenthood, and to other family planning clinics like it.

It’s also not about protecting states from being “forced” to fund Planned Parenthood, as some reporting has suggested. The rule Obama signed in December, and that Republicans are now poised to overturn, was about reinforcing existing law and about protecting the integrity of the nation’s safety net for family planning services.

This is the key thing to understand about what Republicans are doing by overturning Obama’s rule. Yes, they’re empowering some states to defund Planned Parenthood and similar providers, partially, if they choose. But that’s only part of the story. “Defunding” Planned Parenthood in this particular way can cause a devastating domino effect on the larger health care network that low-income women rely on for birth control.

Obama’s rule deals with Title X, one of Planned Parenthood’s two major sources of public funding

The Republican Party has been waging war against Planned Parenthood’s public funding for years now, because they object to the fact that Planned Parenthood provides abortions. Even though federal tax dollars don’t pay for Planned Parenthood’s abortion services, Republicans claim that funding other health care services at the organization indirectly helps fund abortion.

In practice, however, defunding Planned Parenthood takes funding away from its mostly low-income patients — who might be forced to seek care elsewhere if the government stopped subsidizing their visits to Planned Parenthood, and who might face delays and worse care elsewhere if other clinics get overbooked from trying to take on Planned Parenthood’s former patients.

Planned Parenthood receives more than $500 million annually from the federal government. That money pays for specific health services — things like birth control, cervical cancer screening, or STI prevention, but not abortion — for people who couldn’t afford them otherwise.

Most of the funds (75 percent) are actually reimbursements from Medicaid, the US’s public health insurance program for the poor. Just like with any other insurance, Medicaid patients go to their health care appointment first and then have Medicaid pay all or most of the bill later.

The rest of Planned Parenthood’s federal funds come from Title X, the nation’s only federal family planning program. It serves 4 million low-income people every year, about a third through Planned Parenthood. Many Title X patients can’t qualify for Medicaid but still make so little money that they need subsidies for birth control and other family planning services. About half of Title X patients are women of color, and many young women rely on Title X because it protects their privacy.

Title X funds are competitive grants; they are awarded to the best-qualified health providers that are best suited to meet a community’s specific needs.

Every state awards the grants differently. The grants might go to state and local health departments, hospitals, family planning councils, or nonprofits like Planned Parenthood. Then those grantees choose a network of health care providers to work with and help them provide services.

When Planned Parenthood affiliates and clinics earn Title X grants, it’s because they have proven they can administer better care than other local providers.

But 13 states have decided to “defund” Planned Parenthood by finding creative ways to bar the organization from receiving Title X funds — no matter how much more qualified it is to make use of those funds than other providers in the area.

Obama’s rule told states they can’t deny family planning grants to Planned Parenthood just because it provides abortions

At the time Obama signed the new rule, the Health and Human Services Department said that 13 states kicked Planned Parenthood out of their Title X network just because it offers abortions — not for any reason related to its ability to provide Title X health services.

These state restrictions worked in different ways. Some states banned Planned Parenthood, specifically, from getting any grant money. Some of them gave priority to public entities, which was a more indirect way of excluding Planned Parenthood since it’s a private nonprofit.

Either way, according to HHS, the result was a decrease in health services overall, and especially in geographic areas where adequate health care options were more limited.

None of this was actually supposed to happen under federal law. Title X grants were only supposed to be awarded based on how well a provider could offer Title X services. If Planned Parenthood didn’t offer a full range of birth control options, that might be a reason to deny it a Title X grant. Whether or not it uses separate funds, not supported in any way by Title X, to provide abortions should be irrelevant.

But some states still used the Title X program to discriminate against Planned Parenthood anyway. And those efforts even sometimes withstood court challenges.

That’s why Obama signed the new rule in the first place — to make absolutely clear, to both states and courts, that Title X grants are not to be used as proxies in the abortion wars.

It’s not totally clear what would happen if Congress didn’t overturn the rule. Would all of those 13 states have had to change their laws? Maybe, maybe not. But HHS expected the rule to potentially “reverse” the service reductions and deteriorated outcomes that had resulted from those states’ actions.

Title X is much bigger than Planned Parenthood — but it also needs Planned Parenthood in order to function well

Title X is a network. The grant program supports a wide array of health care providers — not just Planned Parenthood and other nonprofit family planning clinics, but also hospitals, community health centers, and local health departments — that provide family planning services to low-income people at reduced or no cost.

Together, Title X and Medicaid combine to form our nation’s family planning safety net. That safety net helped prevent 1.9 million unintended pregnancies in 2014, according to the Guttmacher Institute, and without it the rates of unplanned birth and abortion would have each been 68 percent higher.

Research from the Guttmacher Institute, a think tank that studies reproductive health issues, shows Planned Parenthood plays a pivotal role in the family planning safety net that can’t easily be replaced.

For instance, because it specializes in reproductive health care, Planned Parenthood is usually much better at providing birth control than other clinics that focus on primary care:

And in many areas of the country, Planned Parenthood is the only nearby place where low-income women can get subsidized birth control:

When they argue to defund Planned Parenthood, Republicans usually insist that women’s health care would not suffer as a result. They say that Planned Parenthood’s public funding can simply be diverted somewhere else — to the nation’s many community health centers, for instance, which vastly outnumber Planned Parenthood clinics nationwide.

But while many community health centers offer high-quality care, there is just no way that most of them could take on Planned Parenthood’s patients if the organization shut down. They don’t have the capacity; they often struggle just to accommodate the patients they already have, and it would take years of capacity building for more money to actually solve that problem.

And that’s if Republicans actually keep their promises to divert Planned Parenthood’s funding elsewhere. That often doesn’t happen. And when it does, it often doesn’t work.

After Republican lawmakers in Kansas kicked Planned Parenthood out of the state’s Title X program by restricting the grants to public entities in 2011, the number of patients seen in Title X–funded health centers in Kansas dropped dramatically, from 38,461 patients in 2011 to just 24,047 in 2015.

When Republican lawmakers in Texas kicked Planned Parenthood out of the state’s Women’s Health Program in 2013, other providers didn’t step up to fill in the gaps. Women just got less health care. In areas that had been served by Planned Parenthood before defunding, prescriptions for the most effective forms of birth control plummeted by a third, and women on Medicaid had 27 percent more births than normal.

The success of the Title X program as a whole depends significantly on Planned Parenthood’s ability to participate in it. Think of the Title X network as a sweater with pink stripes, where the stripes are Planned Parenthood. If you hate pink and try to yank the stripes out of the sweater, you risk unraveling the whole thing. And in the best-case scenario, you just get a sweater that’s full of holes and doesn’t keep you nearly as warm anymore.

Republicans tell women they can “go somewhere else” if Planned Parenthood is defunded. But they keep trying to defund the “somewhere elses,” too.

The Title X program is woefully underfunded as it is, and for six years the Republican-dominated Congress has refused to increase its budget for delivering services — even as the need for subsidized birth control went up.

And that’s after Republicans have been forced to compromise by Democrats in the Senate. In every budget House Republicans have proposed over the past seven years, they have called for the total elimination of Title X funding.

There’s a cruel irony in this. Again, because many Republicans don’t want to be seen as actively hostile to women’s health, they often claim that women could just “go somewhere else” for reproductive health care if their local Planned Parenthood shut down due to defunding.

Usually, the “somewhere else” Republicans praise the most is our nation’s vast network of thousands of federally qualified health centers and other publicly funded health care providers.

But that network is funded by Title X, the program that Republicans keep trying to weaken by kicking Planned Parenthood out of it — or eliminate entirely.

Anti-abortion Republicans sometimes act like abortion is so morally toxic that any money flowing anywhere near it becomes tainted. Title X’s family planning services, it seems, are tainted by Planned Parenthood, because Planned Parenthood is tainted by its abortion care — never mind that this care isn’t paid for by tax dollars.

This obsession with financial “purity” means that contraception and other family planning services get thrown under the bus.

Some Republicans may think that contraception itself is a moral evil; others may just think it’s acceptable collateral damage in the war on abortion. A few Republicans want no part in a messy funding fight. Still others may really believe their own unlikely story about how if Planned Parenthood went out of business, women could just go somewhere else for care.

But in today’s Republican Party, the moral imperative to stamp out public funding for Planned Parenthood has completely trumped the moral imperative to make sure low-income women, and men, can get comprehensive reproductive health care.