The Patient Protection and Affordable Care Act, aka “Obama-care,” is clearly unaffordable.

But the notion of South Carolina nullifying it is clearly unconstitutional — and thus impractical.

So even South Carolinians who correctly decry that federal behemoth as a costly, intrusive, big-government debacle should oppose the “Freedom of Choice in Health Care Act” now before the S.C. Senate.

Passed by the House last month, the misguided bill is on “special order,” which has moved it up on the Senate’s agenda as the scheduled end of the legislative session looms this afternoon.

The wiser course in countering Obama-care has already been taken by Gov. Nikki Haley. She, with the Legislature’s backing, has made the choice, allowed under that federal law, to decline its offered vast expansion of Medicaid eligibility in our state.

Yet in theory, if the nullification bill is passed by the Senate and signed into law by Gov. Haley (and there’s no guarantee she would do so), it would effectively void the entire Affordable Care Act in South Carolina.

In fact, though, that legislation would trigger a costly — and losing — court fight that would make South Carolina’s Obama-care opponents appear at best foolish, at worst detached from legal reality.

Don’t take our word for it.

Take the Founding Fathers’ words for it in Article VI of the U.S. Constitution:

“This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”

In other words, the “supreme Law of the Land” overrides the “Laws of any State.”

The U.S. Supreme Court has repeatedly confirmed that standard. And last summer, generally conservative Chief Justice John Roberts helped uphold Obamacare against a far more substantive constitutional challenge, from 26 state attorneys general (including our own), than a nullification bill.

Yes, there’s a strong case to be made against Obamacare. For instance:

■ President Barack Obama pushed it through Congress in 2010 without a single Republican vote while repeatedly —and wrongly — assuring Americans that if they liked their health insurance plans, they could keep them if the bill passed.

■ Even U.S. Senate Finance Committee Chairman Max Baucus, D-Mont., called the law’s looming implementation a “huge train wreck” less than two months ago.

■ The administration has granted waivers from the law’s oppressive, expensive and job-killing regulations to more than 1,500 private and public entities, including big businesses and big unions.

■ The increasingly disgraced Internal Revenue Service is supposed to enforce many of its onerous mandates.

However, those flagrant flaws in the national law don’t create a nullification opening. And considering South Carolina’s unpleasant history on defiance of federal authority, our state lawmakers should know better (see former S.C. State Professor William C. Hine’s column on today’s Commentary page).

But just because South Carolina can’t constitutionally nullify Obamacare doesn’t mean we can’t make a principled — and sustainable — stand against that massive 21st century manifestation of Nanny State folly.

Gov. Haley and the General Assembly have done just that by rejecting Washington’s Medicaid-expansion plan. They rightly concluded that while the law provides federal funding for the expansion over the short term, the increase would impose unacceptable long-term financial obligations on our state.

As for the nullification bill, this week Gov. Haley’s office ducked the question of whether she would sign it. Instead, her spokesman reiterated that her top priorities for this legislative session remain blocking Medicaid expansion and advancing state-government restructuring and ethics reform.

Ethics reform and government restructuring have yet to be finalized. Both are worthy, realistic goals.

Imagining that our state can nullify the law of our nation is not.