Health-care reform is a key campaign issue, but there's at least one program neither presidential candidate is talking much about: Medicare. It's hugely popular, but rising costs and aging boomers are straining its finances. What would a President McCain or President Obama do about that—and how smart are their plans? NEWSWEEK's Mary Carmichael spoke with Joseph Newhouse, a Medicare expert and professor of health policy at Harvard University:

NEWSWEEK: Why is Medicare taking such a back seat in this election?
NEWHOUSE: Because it's an issue that will only lose you votes. The elderly vote at high rates, and Medicare is a voting issue for them, so it's very heavy political lifting to cut benefits or services.

But it's a pressing problem. According to one report, the trust fund that covers hospital stays will start running out in 2011 and be gone by 2019.
Well, the present trend is not sustainable, but there is a lot of uncertainty about when the trust fund will run out. The key number driving the forecasts is the rate of increase in health-care costs, which can change. Think of what would happen if in three years we had an effective drug for Alzheimer's disease.

It could drive Medicare costs up and the funding could run out even sooner.
On the other hand, maybe medical innovation will slow down in the future, and costs won't rise so steeply.

We do know of one trend for certain—the boomers are getting older.
True, but in terms of when the trust fund runs out, that is less of a problem than the increase in costs per beneficiary. Look at Social Security—it probably won't run out until the 2040s. That's because it's subject only to boomers becoming eligible, whereas Medicare is subject to both that phenomenon and to rising health-care costs.

You're written some provocative things about the rise in health-care costs—specifically, you don't think it's all bad.
A lot of the discussion has been, "Oh my God, the sky is falling, we have to stop the increase in costs." My own view is that we can talk about inefficiencies and how money can be saved—and I agree with a lot of that talk—but the higher costs have come with a lot of benefits: devices like artificial hips and knees, traditional drugs like antidepressants, new biotech drugs, new procedures. A lot of that innovation is what has made medicine more expensive. So any simplistic attempts to control costs may risk jeopardizing future innovation.

But innovation isn't the only culprit. You reported earlier this year that prices for some drugs used by the elderly have gone up almost 25 percent in the past two years.
What happened was that a substantial chunk of the elderly gained drug benefits. Then their demand for brand-name drugs went up, so the drug manufacturers responded by increasing their prices.

Should Medicare have price controls, then? Obama has said they would save billions.
The government can't be in the position of paying any price that a manufacturer names, so in the cases where a drug has no competition, there ought to be some kind of ability to set prices. But price controls could also spook venture capital and drive it out of the drug industry.

What about McCain's reforms? Let's start with means testing—he recently proposed a small increase in premiums for prescription-drug coverage for those making more than $160,000 a year.
Well, there's some means testing in Medicare already. The bigger problem is that the high-income group is a very small percentage of the elderly. There aren't enough of them to make much of a dent if the goal is to save money. And it's hard to even say what their incomes are, because the elderly are mostly living off their assets, like their homes. Means testing on that basis is very difficult.

McCain also says that "Medicare should not pay for preventable medical errors or mismanagement." Is that another reform that's already been put in place?
It was just announced in the last year that Medicare will no longer pay for hospital errors. This is also a tricky proposal, and I would not expect a lot of savings from it. Medical errors can be hard to detect, at least at a level of certainty to justify non-payment. And saying you won't pay for errors has a potentially perverse effect. If you're trying to mitigate errors, you want everything out in the open so you know what is causing the problems.

If you're a doctor and you know admitting to error means you won't get paid—
You may instead try to get away with not reporting it.

There's at least one Medicare reform neither candidate has proposed: raising the age of eligibility.
There's an obvious political reason to avoid that, and a couple of substantive ones as well. Raising the age of eligibility doesn't save as much money as one might think, because those first years under Medicare are the cheaper ones when people are in their best health. Also, one of the important subgroups of the uninsured are the so-called near-elderly, who are around age 60. By raising the eligibility age for Medicare, you potentially increase the size of that uninsured group.

People have been calling for serious Medicare reform for decades. It hasn't happened. Is there reason to think the next four years will be any different?
Not really. The historical record suggests that if it looks possible to make some modest changes and put the big ones off to another Congress, that's what Washington will do. But at some point, of course, that will no longer be possible.