During the Oct. 2 VP debates, as Joe Biden was explaining about John McCain's health care plan, someone at the table next to mine yelled out, "I don't understand all those stupid numbers!" It's not that hard, and it's important.

McCain proposes to grant a tax credit that is used to buy health insurance. From his Web site: "Every family will receive a direct refundable tax credit - effectively cash - of $2,500 for individuals and $5,000 for families to offset the cost of insurance. Families will be able to choose the insurance provider that suits them best and the money would be sent directly to the insurance provider."

OK, so it's not really "cash"; you won't ever see it. But never mind that. Under the McCain plan, your family would take that $5,000 you're not spending on taxes, and spend it on health insurance instead. You would not have the option to spend it on, say, credit card debt or your child's education.

Biden pointed out that McCain's plan eliminates the current tax break for employers' health insurance payments. That is, you pay $5,000 less in taxes if you buy health insurance, but your employer can no longer deduct the $7,000 to $12,000 it pays for your health insurance. Employers are always looking for ways to cut costs, and unions have little leverage any more, so it seems very likely that many employers will cancel their health insurance benefits.

A recent study by university researchers at Columbia, Purdue, Michigan and Harvard estimates that 20 million families who are currently insured will lose their coverage if the McCain proposal is implemented. They write, "Moving toward a relatively unregulated nongroup market (as McCain proposes) will tend to raise costs, reduce the generosity of benefits, and leave people with fewer consumer protections."

I think 20 million is a low estimate, but let's run with it for the sake of illustration. Those 20 million families will lose health insurance that costs roughly $12,000, on average. They will lose it because their employers can save a lot of money that way. They must replace their coverage, but they only have $5,000 to replace it with. Do you know of an insurance company that will give you $12,000 worth of coverage for $5,000?

These families could decide to pay the extra $7,000 themselves, adding this amount to the tax credit and thus replacing their lost $12,000 policies. The Census Bureau's 2007 income statistics tell us that half of American households bring home less than $50,000 a year. Now subtract the $7,000-plus extra cost of health insurance, and taxes, and there's precious little left to live on, much less save for the future.

But there's a bigger problem: these families will no longer be eligible for group plans, which spread risk over a large number of people. This means that insurance companies can deny them coverage for any reason whatsoever. If they have any "pre-existing conditions," that is, if they actually need health insurance, they will certainly be denied coverage.

Point of fact: an ordinarily healthy 22-year-old college graduate I know was recently denied individual coverage because he has "sports asthma," which basically means that he has to avoid running and exercise in other ways.

McCain's answer to this virtually certain denial of coverage is to "work with governors" to implement "state best practices" to get everyone covered. Perhaps he intends to emulate Massachusetts' universal coverage, which likely is the current best practice among states. Somehow, though, I think not.

Many millions of American families are one illness, one accident or one surgery away from financial ruin. Many have already been ruined. Many more will become eligible for ruin under a McCain administration.

There are those who argue that markets always work. This is the bill of goods we have been sold in this country for the last 35 years - and it bears no resemblance to economic or societal facts. Markets fail to control monopoly, secure fairness, and protect against harms.

Nevertheless, the market torch-bearers maintain that people without health insurance are simply unwilling to pay its cost. This may be true, but so what? People also need food, warmth, shelter, clothing, transportation and education.

My friends, it is not right that we live in this wealthy nation and have 42 million people with no health insurance. To throw another 20 million-plus families - that's 60 or 80 million people - off the health care rolls would be to compound the wrong, not to correct it. Please - think about it.