Health care premiums would shoot way up for everyone, because all the sick people get coverage and the healthy people don’t sign up. Subsidies could become a huge drain on the federal treasury, creating another entitlement that’s politically impossible to roll back. Businesses might drop health coverage and send their workers to the health exchanges — overloading the exchanges and driving up costs even more.

Making things worse, more low-wage workers could see their hours get cut back so the employers don’t have to cover them. States that expand Medicaid would then get stuck with the bill as the feds break their promise to pick up just about all of the new costs.

There’s also a new danger for Obama now that so many governors have refused to set up their own state health exchanges. The federal government will have to run exchanges for them, and the worst-case scenario would be that the Obama administration isn’t up to the task…

What really worries advocates of the law in the short term, though, is the prospect that Obama might agree to pare the law’s consumer subsidies before they begin — one concession he could give Republicans as part of a deal to head off automatic spending cuts or a government shutdown.

“That’s definitely a worst-case thing for anyone who worked on the law,” said Dash — because the law will only work if the subsidies make the coverage affordable to the people who have to buy it.