Americans for Prosperity, the small-government group financed by Charles and David Koch, is running an ad campaign about Obamacare. You're not going to believe this, but they stretched the truth a bit.

Rating the accuracy of political ads is a mug's game -- not because those campaigns are full of untruths and half-truths, which they tend to be, but because it's highly uncertain that truthfulness is even an aspiration. As the philosopher Harry Frankfurt has explained, the goal of the form isn't deceiving your audience about what's true and false, so much as making the distinction so confusing as to be irrelevant.

By that definition, this latest AFP campaign is a work of art. It includes a 30-second television commercial in which a woman, called Julie, recounts how her son suffered seizures, notes that the medical care he got "meant the world to me," and says she has some questions about the Affordable Care Act. Of course, she doesn't have questions; instead, she makes three cunningly deceptive assertions about the law, disguised as questions.

The first is 98 percent false. "If we can't pick our own doctor," she asks, "how do I know my family's going to get the care they need?" Hang on a second: Who said anything about not being able to pick your own doctor? Not the law, which contains no such provision.

The closest you get to this scenario are managed-care plans that restrict people's ability to pick out-of-network doctors, which is a common feature of the existing insurance market. Those plans may become more common or more strict as a result of the law, though it's hardly guaranteed. But if you think insurance networks are an infringement on your liberty, you'd better move to Canada, or some other place with a single-payer system.

Next, the woman asks, "What am I getting in exchange for higher premiums and a smaller paycheck?" This is a half-truth sandwich. Yes, Obamacare probably will increase premiums for some people by limiting higher charges for older beneficiaries, and through a tax on insurers that may be passed on to employers. But the tax doesn't apply to companies that are big enough to insure themselves, which was 59 percent of all private-sector employees in 2011.

If you work for one of those companies that self-insures, you may see higher premiums if your company now offers lousy insurance and has to provide something more comprehensive. Will you see a smaller paycheck as a result? Maybe, but not for nothing. (Shouldn't everyone be entitled to quality care if their child has seizures, Julie?) If you're working for a company that doesn't self-insure and whose insurance is subject to the insurance tax, that company might decide to absorb higher premiums through smaller paychecks, rather than passing on higher premiums to its employees. But if that's the case, then a greater decrease in pay means a lesser increase in premiums. And if your company already offers good insurance and self-insures, your premiums may not rise any faster than they already were.

Finally, Julie asks, "Can I really trust the folks in Washington with my family's health care?" Now, unless her doctors are located in the nation's capital, this statement is pure fiction: Obamacare doesn't empower anyone in government to dictate the health-care services people receive. But it's a catchy fiction, and conservatives have done a good job of repeating it in the face of all evidence. It's barely even a claim anymore; it's more like a catchy tune you heard on the radio and can't stop humming.

But the most devious part of the ad is found in the phrase, "What am I getting?" Before Obamacare, if Julie's family got health care through an employer (which the ad strongly implies), then her son's medical condition might have made it prohibitively expensive to buy insurance on the individual market. So what she's getting with Obamacare is the freedom for her or her spouse to leave their job -- to start a business, perhaps -- without being locked out of insurance. A 2011 government study found that 1 in 2 Americans could be affected by pre-existing condition exclusions if the law were repealed.

The ad might have a more compelling case if the woman didn't have a son with a pre-existing condition. Her question -- "What am I getting?" -- would then take on a much more direct tone: What am I, a person who has insurance, getting from a law that provides insurance to people who don't? How does it hurt me if they can't get care?

If anything, this is where Americans for Prosperity stumbles: It's hard to think of a better advertisement for Obamacare than the blind selfishness of some of its opponents.

(Christopher Flavelle is a member of the Bloomberg View editorial board. Follow him on Twitter.)