Now that U.S. health care has been annexed by Washington, every medical question will soon become a political question too, and the British elections are foreshadowing what that will mean in practice. Over the weekend, David Cameron and the Conservatives promised that if they win in May they’ll devote £1 billion to ensuring that National Health Service patients have access to cutting-edge cancer treatments.

The Tories say the £200 million annual fund will pay for drugs that have been prohibited or controlled by Britain’s rationing bureaucracies, and give physicians more latitude in deciding which drugs to prescribe, especially for rare cancers and orphan diseases. Cancer survival rates in Britain lag behind the rest of Europe, and especially the U.S., but the Tory proposal is, believe it or not, controversial.

The Labour government says the plan is unaffordable. Meanwhile, “It’s wrong to recommend the use of treatments where the additional benefit is uncertain,” Andrew Dillon told the Guardian. “This is misleading for patients and wastes scarce NHS resources.”

Sir Andrew leads the National Institute for Health and Clinical Excellence, or NICE, the body that makes hard-and-fast decisions about which patients will benefit from which treatments, and which lives are cost-effective to save or improve amid a tight budget. Recent NICE rejections include the bone-marrow drug Vidaza, multicancer drug Avastin, and Tyverb for breast cancer. Sutent, a breakthrough treatment for kidney cancer, was only approved after a campaign by doctors, against NICE’s supposedly better judgment.

One of ObamaCare’s core promises is that American technocrats will also use medical evidence to control health spending, but the British experience neatly illustrates the inevitable outcome. In the medical journal Lancet Oncology in 2008, researchers produced the first direct world-wide comparison of five-year survival rates for breast, colorectal and prostate cancers. The U.S. had the highest survival rate for breast cancer at 83.9% and prostate cancer at 91.9%—compared to the U.K.’s respective 69.7% and 51.1%.

While the data are from the 1990s, and British outcomes have since improved somewhat, the authors conclude that “Most of the wide global range in survival is probably attributable to differences in access to diagnostic and treatment services.” In other words, advanced tests and drug treatments result in better outcomes.

That kind of innovative health care is costly, and the inescapable logic of a health system dominated by government is that it always ends up with some version of NICE. Scarcity forces choices, which have long been especially severe in Britain where austerity medicine is the norm. Mr. Cameron deserves credit for trying to ameliorate the worst excesses of a system that pits the terminally ill against, say, strep throat.

The open-ended style of American care has the problem of rapidly growing costs, but as the British spectacle shows it is extremely difficult to reverse a command medical economy once it is entrenched, even when the results are morally appalling. The far better option is to extricate politics and give patients more control, which starts by rolling back ObamaCare.