NASHVILLE — Republican John McCain and Democrat Barack Obama offered radically different responses to what was arguably the best question asked so far in any of this year’s debates.

Addressing Obama, a woman in the studio audience at the second presidential debate on the Nashville campus of Belmont University said, “Senator, selling health care coverage in America as the marketable commodity has become a very profitable industry.”

Then, she asked, “Do you believe health care should be treated as a commodity?”

Obama responded at some length, without actually answering the question.

McCain did the same.

Moderator Tom Brokaw pressed the point.

“Quick discussion: Is health care in America a privilege, a right, or a responsibility?” said the NBC newsman. “Senator McCain?”

“I think it’s a responsibility,” responded the Republican nominee for president.

McCain then rambled through a torturous attempt at an answer, ranting about “government mandates” and griping about the requirements that would, necessarily, go with any univeral program to provide health care for all.

Brokaw then turned to Obama.

“Well, I think it should be a right for every American,” the Democrats declared. “In a country as wealthy as ours, for us to have people who are going bankrupt because they can’t pay their medical bills — for my mother to die of cancer at the age of 53 and have to spend the last months of her life in the hospital room arguing with insurance companies because they’re saying that this may be a pre-existing condition and they don’t have to pay her treatment, there’s something fundamentally wrong about that.”

On a night when both candidates continued to dance around the economic crisis — more frequently pointing fingers of blame than offering programs for renewal — and when they repeated their stances on foreign policy issues involving Iraq, Iran, Israel, Afghanistan and Pakistan, the essential line of distinction was drawn by the candidates themselves on the essential issue of health care reform.

At a point in the American journey when tens of millions of Americans have no health care coverage, when tens of millions of additional Americans have insufficient coverage and when tens of millions more worry about losing not just a job but the health care benefits that go with employment, the difference between a candidate who says that health care is “a right” versus one who says that it is “a responsibility” could not be more stark.

Obama referred to “this fundamental difference,” and he was correct.

It is easy, and appropriate, to criticize Obama and McCain for offering inperfect, and inadequate, proposals for addressing this country’s health care crisis. Neither man supports the single-payer health care reform that really would provide care for all while controlling prices.

But as the two contenders outlined their proposals for health care reform, the depth of their difference became clear.

McCain said, “(What) is at stake here in this health care issue is the fundamental difference between myself and Senator Obama. As you notice, he starts talking about government. He starts saying, government will do this and government will do that, and then government will, and he’ll impose mandates.”

In particular, the Arizonan griped about rules that limit the ability of insurance companies to sell policies across state lines.

Obama explained why the rules matter.

“(The) reason that it’s a problem to go shopping state by state — you know what insurance companies will do, they will find a state — maybe Arizona, maybe another state, where there are no requirements for you to get cancer screenings, where there are no requirements for you to have to get pre-existing conditions, and they will all set up shop there,” began the senator from Illinois.

Then he landed the bluntest blow.

“That’s how in banking it works,” said Obama. “Everybody goes to Delaware, because they’ve got… pretty loose laws when it comes to things like credit cards. And in that situation, what happens is… that the protections you have, the consumer protections that you need, you’re not going to have available to you.”

“That,” he concluded, “is a fundamental difference that I have with Senator McCain. He believes in deregulation in every circumstance. That’s what we’ve been going through for the last eight years. It hasn’t worked, and we need fundamental change.”

That comparison of McCain’s response to the health-care crisis — deregulation — with the missteps and misdeeds that created the current financial crisis was as spot on as it was devastating.

When it comes to the health care debate, these candidates are not two sides of the same coin.

Barack Obama believes that health care is a right — something every American should be able to access when they are in need of care.

John McCain believes that health care is a responsibility — a burden that some Americans will be able to shoulder while some will not.

Access to adequate health care is not just about check ups and medical care. It is about the quality of our lives. And, ultimately, about life and death. That makes health care a moral issue.

Barack Obama recognizes this fundamental fact.

John McCain does not.