Next Friday’s omnibus budget deadline may be Congress’ last best chance for passing a bill to stabilize Obamacare’s volatile individual market and prevent premiums from shooting up just before November’s midterm elections. But the bipartisan effort that has dragged out since last summer may crumble in the face of opposition from conservative lobby groups and demands from President Trump and House Republicans that Democrats say are “poison pills.”

Even if Congress manages to pass some form of the bipartisan package lawmakers have spent months negotiating—restoring the cost-sharing reduction (CSR) payments to insurers terminated by the Trump administration last year and implementing a national reinsurance program—health care experts and some lawmakers say that won’t do enough to stop the bleeding.

“When Alexander-Murray was originally crafted and we all signed onto it on a bipartisan basis, the sabotage was still limited,” Sen. Tammy Baldwin (D-WI) told TPM in a sit-down interview in her office Tuesday. “There’s been so much more since then, so what might have been much more than a Band-Aid right now is more limited in how much it can do.”

Read the latest reporter’s sum-up (Prime access) on GOP efforts to undermine Obamacare »

Baldwin said that since senators began drafting the Obamacare stabilization bill last year, the Trump administration and Republicans in Congress have taken many additional steps to hack away at and generally undermine the individual market.

The Trump administration cut off billions in CSRs, cut the open enrollment window in half, defunded open enrollment outreach, and signed an executive order allowing the sale of cheap short-term plans and Association Health Plans that flout ACA regulations. Meanwhile, the GOP-controlled Congress repealed the individual mandate. These steps combined are expected over the next several years to increase the number of uninsured people by as many as tens of millions, and drive up insurance premiums by double digits.

Baldwin told TPM that if Congress re-funds the CSRs and passes a temporary reinsurance program but ignores the threat of the short-term plans, it would be like bailing out a sinking ship while failing to patch a hole in the hull.

“It creates a gaping hole, especially for those who have pre-existing conditions,” she said, “And if you make short-term plans into long-term plans, it’s a huge step in the wrong direction.”

President Trump signed an executive order in February lifting the three-month cap on short-term, off-market plans that aren’t bound by the ACA’s rules and can turn away people with pre-existing conditions or charge them higher premiums. The plans, which will now be allowed for nearly a full year, are also allowed to charge women more, and can refuse to cover Essential Health Benefits prescription drugs or emergency room visits.

“I think it will not only have the impact of basically allowing junk plans to be offered to sometimes unsuspecting people, but beyond that, it will drive up prices in the ACA marketplace because healthier people may go into the junk plans and leave older and less-well people in the ACA,” Baldwin told TPM.

Baldwin’s bill would roll back Trump’s executive order, returning the three-month limit to such plans. It would also force the plans for the first time to comply with some Obamacare rules, meaning they would have to cover essential health benefits and preventative services, couldn’t turn someone away or charge them more because of their gender or a pre-existing condition, and couldn’t set annual or lifetime limits on their care costs.

The 2018 open enrollment season was successful beyond health care advocates’ wildest expectations, nearing numbers from previous years despite the Trump administration’s rollbacks. But Baldwin is warning that without legislative intervention, 2019 could see rising costs and plunging enrollment as a combined result of the lure of the short-term plans and the repeal of the penalty for those who go without insurance.

“Unless Congress is able to act to really stabilize the market in a really comprehensive way, we’re going to see a real impact from the administration’s changes,” she said.

Whether Baldwin’s bill or any ACA stabilization measures at all will be included in next week’s omnibus is not yet certain, and the prospects are looking dimmer by the day. As with bipartisan efforts to pass a bill to protect DACA recipients and implement some forms of gun control, the President’s initial enthusiasm and vocal support for the health care package has given way to skepticism and demands for new conservative provisions.

When asked by TPM on Tuesday if the stabilization package will be a part of the omnibus budget, House Minority Whip Steny Hoyer (D-MD) said that unless Republican and Democratic leaders can agree to include it, it’ll have to sink or swim on its own.

“Obviously we think we need to stabilize the market,” Hoyer said. “And historically, it’s been easier to put things like that in a big bill and move them all at one time. But if it’s an item in disagreement, it will have to be moved individually.”