There is a familiar hiccup in the ongoing negotiations for a long-term government spending bill: federal funding for Planned Parenthood.

Politico revealed on Wednesday that House Republicans are insisting on fully defunding the women’s health organization — long vilified by conservatives because some of its clinics perform abortions — in the spending package that lawmakers need to pass before March 23.

From Jennifer Haberkorn and Sarah Ferris:

The riders would cut off federal funding to Planned Parenthood, eliminate a federal family planning program and ax the Teen Pregnancy Prevention Program, according to sources on Capitol Hill. Republicans also want to insert a new prohibition on funding research that uses human fetal tissue obtained after an abortion.

The proposal actually goes further than previous GOP attempts to defund Planned Parenthood, Politico noted. Previously, Republicans just wanted to cut off Medicaid dollars used for cancer screenings and other routine health care for the group (federal law already prohibits direct funding of abortion under the Hyde Amendment). This latest proposal would block Medicaid and several other federal funding sources, a full cutoff of federal dollars going to the organization.

Experts say defunding Planned Parenthood would lead to more unplanned pregnancies and would mean fewer women, particularly low-income women, would have access to basic health care.

Whenever Republicans have power and a spending bill comes up, they want to defund Planned Parenthood. It’s one of their signature issues. But those gambits usually fail because, while Republicans can pass anything they like in the House with no Democratic votes, they are going to need Democratic support to pass a spending bill in the Senate.

Democrats aren’t budging, and they’re alleging that Republicans surprised them with the last-minute demands, according to Politico:

Democrats say an agreement was near on overall funding levels for the fiscal 2018 Labor-Health and Human Servies funding measure, typically one of the most contentious spending bills. But when top appropriators met to finalize the numbers, the Democrats said Republicans reneged on women’s health issues, according to Democratic sources familiar with the talks.

The simple math of the matter is: A spending bill needs 60 votes in the Senate, there are 51 Republicans, and so they need at least nine Democrats to join them. It seems unlikely that there are nine Senate Democrats who would vote to defund Planned Parenthood. That’s why the GOP’s dreams have never come true.

And if you read the Politico report closely, top Republicans seem to know they can’t win. Sen. Roy Blunt (R-MO), who oversees health care spending in the Senate, more or less said that the final spending bill would need to be something palatable to Democrats.

But the impasse is serious enough that lawmakers have reportedly started discussing whether they would need to pass another short-term spending bill before March 23 — it would be their sixth since the fall — to avoid a government shutdown over the issue.

But the end game seems to be, inevitably, that Republicans would have to fold. But that doesn’t mean Planned Parenthood is out of danger: As Vox’s Anna North reported recently, the Trump administration is doing what it can to help states block funding for the group.