The idea is deceptively simple: Because President Barack Obama promised Americans they could keep their existing insurance under his new health-care-reform law, Congress should pass a law guaranteeing that they can.

In reality, though, Obama was wrong to have made that promise -- and Congress would be compounding his foolishness by forcing insurance companies to keep it. The primary goal of the Patient Protection and Affordable Care Act is to make the health-care system more efficient and comprehensive. It has never been to preserve individual insurance plans.

Recall that the reason the president’s promise was so dumb is that it was not his to make. That is, the federal government cannot force insurers to offer policies they do not want to sell. What it can do, however, is set a minimum level of benefits (preventive care without copayments, for example) and require that they be offered at the same price to everyone, even people in poor health. And it can create a marketplace to allow people to compare plans and coverage.

This is, in fact, what the Affordable Care Act does (or tries to; its glitchy federal marketplace has allowed only about 27,000 people to get private insurance so far). Some insurance companies thus decided to stop selling policies that did not meet these criteria -- or, alternatively, to improve their policies but raise prices.

As a result, hundreds of thousands of people who buy health insurance on their own -- not through an employer -- are seeing their policies canceled. For the most part, these are either people who are healthy enough to have been offered affordable premiums for decent insurance or people who bought low-cost insurance that doesn’t cover basic or unforeseen health-care bills.

Allowing them to keep these policies -- as two congressional proposals would do -- causes practical and policy problems. On the small side are the headaches it creates for insurance companies, which have already canceled their plans and laid the groundwork for complying with the new law. A much bigger problem is that healthy people would be kept from joining the risk pools for policies sold on the exchanges, boosting costs for insurers and leading them, in turn, to raise prices.

The two proposals before Congress are deficient in almost opposite ways. The bill introduced by Representative Fred Upton, a Republican from Michigan, would allow an insurer to keep selling policies through 2014 that it offered on Jan. 1, 2013 -- even to people who don’t already have those policies.

This bill would not force insurers to keep selling those policies, however, and many might remain canceled. The result would be that, for some people, Upton’s Keep Your Health Plan Act would be guilty of making the same false promise that Obama did.

The bill from Senator Mary Landrieu, the Louisiana Democrat, would require insurers to keep selling any policy sold on Dec. 31 of this year for as long as the customer wants to keep it -- unless the insurer gets out of the health-care business altogether. It’s hard to imagine such a coercive measure passing. Not only would insurers -- which change their policies all the time -- resist, but such an imposition on the private market would also surely enrage Obamacare’s opponents.

One of the virtues (or defects; choose one) of Obamacare is that it would disrupt the health-insurance market. Some people would not be able to keep their insurance under the law, and Obama was wrong to say otherwise. Instead of doubling down on his promise, Congress should keep the pressure on the administration to fix the law’s website, whose pathetic performance was officially detailed today. At least that way, those who have lost their insurance will have a better idea of what their options are.

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