Late in tonight's press conference, President Obama got a question that just begged for an easy, evasive answer. The question was whether he was prepared to promise Americans that, under his reform plan, "the government will never deny any services, that that's going to be decided by the doctor and the patient, and the government will not deny any coverage."

The easy, evasive answer would have been to agree: "Of course we'll cover whatever your doctor recommends." Or Obama could have sidestepped the question, by offering some bland statement of support for the medical community: "We revere phyisicans and want them at the center of our health care system."

But Obama didn't give those answers. Instead, he answered truthfully.

Can I guarantee that there are going to be no changes in the health-care delivery system? No. The whole point of this is to try to encourage changes that work for the American people and make them healthier. And the government already is making some of these decisions. More importantly, insurance companies right now are making those decisions. And part of what we want to do is to make sure that those decisions are being made by doctors and medical experts based on evidence, based on what works. Because that's not how it's working right now. That's not--that's not how it's working right now.

Tomorrow's headline will probably focus on the length of Obama's professorial answers, the small bits of news in his press conference*, and the fact that he seemed genuinely pissed off about what happened to his friend, Henry Louis Gates, in Cambridge the other day. But the most striking thing to me was Obama's willingness--in that question about doctors and a few others--to speak candidly about his health plan, even if that meant giving openings to some of his critics.

Consider that Obama's mission tonight was actually very straightforward: to build support for health reform at a time when it is moving through Congress but, for the first time, running into serious obstacles. To accomplish this, Obama basically had two options at his disposal. He could reassure the public by minimizing the scope of change he was promoting or he could persuade the public by convincing them change, even extensive change, was actually necessary.

In the past, Obama has frequently emphasized the former approach. And at times tonight, he did it again--most clearly when he repeated his promise that people could keep their insurance if they liked it.

But Obama spent most of his time this evening explaining why things had to be different. He did this, first, by talking about the problems of the status quo. He talked about rising premiums, dwindling benefits, and growing costs that are strangling employers and government alike. Invoking a line of reasoning that first emerged in a Steven Pearlstein Washington Post column, Obama said

If somebody told you that there is a plan out there that is guaranteed to double your health-care costs over the next 10 years, that's guaranteed to result in more Americans losing their health care, and that is by far the biggest contributor to our federal deficit, I think most people would be opposed to that. Well, that's the status quo. That's what we have right now. So if we don't change, we can't expect a different result.

He also connected health care to the financial squeeze Americans have been feeling for a long time, even before the present downturn

One of the things that doesn't get talked about is the fact that when premiums are going up, and the costs to employers are going up, that's money that could be going into people's wages and incomes. And over the last decade, we basically saw middle-class families; their incomes and wages flatlined.

But it was later, when the discussion got into policy specifics, that Obama seemed determined to convince people that transformation was a good thing. Consider this question, which--again--focused on the importance of reducing unnecessary medical treatment:

When you describe health-care reform, you don't--understandably, you don't talk about the sacrifices that Americans might have to make. Do you think--do you accept the premise that other than some tax increases, on the wealthiest Americans, the American people are going to have to give anything up in order for this to happen?

Once again, Obama could have changed the subject or offered a bland denial. Once again, he did nothing of the sort.

They're going to have to give up paying for things that don't make them healthier. And I--speaking as an American, I think that's the kind of change you want.

Look, if right now hospitals and--and doctors aren't coordinating enough to have you just take one test when you come in because of an illness but instead have you take one test; then you go to another specialist, you take a second test, then you go to another specialist, you take a third test; and nobody's bothering to send the first test that you took--same test--to the next doctors, you're wasting money. You may not see it, because if you have health insurance right now, it's just being sent to the insurance company, but that's raising your premiums, it's raising everybody's premiums. And that money, one way or another, is coming out of your pocket, although we are also subsidizing some of that, because there are tax breaks for health care. So not only is it costing you money in terms of higher premiums, it's also costing you as a taxpayer.

Now, I want to change that. Every American should want to change that. Why would we want to pay for things that don't work, that aren't making us healthier? ...

It will require, I think, patients to--as well as doctors, as well as hospitals--to be more discriminating consumers. But I think that's a good thing, because ultimately we can't afford this.

Telling doctors and patients they need to be more "discriminating" takes a little bravery, at least in this media environment. Critics are already warning about a government takeover of medicine.**

Obama seems to be banking on the fact that Americans will see past such ridiculous charges--and, more important, that they will come around to the idea that, yeah, maybe we really do need to start cutting down on all that unnecessary medical care.

Is he right? I'm way too close to this subject to have the necessary perspective. (And since I was actually in the East Room tonight, I can't even speak to how it all played on television.)

All I know is that Obama wanted to speak to America like adults tonight--and make the case for the reforms he (quite rightly) believes are necessary. Time will tell whether that faith in the public's patience and judgment is well-placed.

*What was the news? It had to do with timing and, perhaps, financing.

**Perils of late-night blogging: I originally referred to a conservative pundit suggesting Obama would let the elderly die once they got sick, the way Eskimos apparently do (or did). I'm now reliably informed that I'm taking that from another quote, not from a conservative, and for a different purpose. In other words, I was wrong about that. I apologize to any conservatives--not to mention any Eskimos--I may have offended.

--Jonathan Cohn