By midnight on April 28—this Friday—the US government needs to get its funding in order, or shut down. Non-essential services will be suspended until Congress reaches a consensus on a spending bill to keep things running.

Normally, when one party controls all the levers of power in Washington, as the Republicans do now, it should have no problem getting a spending bill passed. But with the Republicans split over some of Trump’s more profligate spending plans, and Democrats reluctant to give him any political victories on the eve of his first 100 days in office, a stand-off seems likely.

There are two things Republican negotiators in the executive branch say give them leverage. But a careful look at both suggests that forcing a shutdown over either issue will be a volatile gamble—something that could blow up in the Republican camp while causing little pain to the Democrats.

1. Build the wall!

The White House is asking for at least a symbolic sum to be earmarked for the border wall with Mexico, a project that is estimated to cost at least $22 billion.

At a time of budget stagnation, and with undocumented immigration already falling, not many lawmakers are eager to throw that cash at something that few experts think would be a cost-effective deterrent. A survey of border-state lawmakers (paywall) by the Wall Street Journal suggested support is lukewarm at best among the people who would be directly affected, and doesn’t poll well.

For Democrats, defeating the wall has become symbolically potent. They also see Trump’s essential untrustworthiness reflected in the fact that, after spending months promising that Mexico would pay for the wall, he now says that Congress must use taxpayer money for it and that Mexico will still pay for it, “at a later date” and “in some form.” And in a further sign of weakness, in a recent interview with the Associated Press, he wouldn’t rule out signing a bill that doesn’t include any wall funding.

2. Hold Obamacare patients hostage

Last month Trump said the Affordable Care Act (ACA), Barack Obama’s signature health-care law, was “imploding.” The White House has begun to signal that if Democrats block funding for the wall with Mexico, it will take steps to hasten that implosion.

The ACA includes “cost-sharing reductions”—government subsidies to help poor people afford health insurance for the first time. Some 7 million people qualify for the payments this year, which averaged more than $1,000 per person in 2016, according to the Kaiser Family Health Foundation, making for a total of $7 billion in subsidies. Critics have mounted a constitutional challenge, saying the law wasn’t correctly written to fund them.

These subsidies to consumers are also an effective subsidy to insurers, allowing them to charge more to cover markets that may be less healthy and thus more expensive to cover than expected. Removing them entirely could potentially make the individual health-insurance market collapse.

The White House is now threatening to accede to the demands of conservative Republicans and simply stop delivering the payments. It hasn’t done so yet only because that would cause financial pain to millions of Americans, as well as the politically powerful insurance and hospital industries.

Democrats want Congress to approve a bill that includes the payments—which would effectively kill the lawsuit against the bill by clearly registering Congress’ intent to fund the spending. Some Republicans are willing to extend the subsidies, especially since the recent failure of their own health-care bill leaves them without a defensible alternative should the market indeed collapse.

That leaves the Trump administration threatening to raise the cost of health care for millions of Americans unless Congress finds the cash to build a wall Mexico was supposed to pay for.

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