President Barack Obama announced triumphantly that 8 million people selected a private insurance plan through the health care exchanges created by legislation known as Obamacare or the Affordable Care Act. He added his own interpretation of the numbers: "This thing is working."

At the same time, however, Democratic candidates across the country still see the health care law as a drag on their campaigns in the midterm elections. After four years of trying, there is still no evidence that the president's signature piece of legislation has become popular. If the law was really working, and voters were excited about it, Democratic candidates would be talking about it all the time, rather than trying to change the subject.

There's a simple rule to evaluate contradictions like this. When the numbers and the behavior disagree, there's something wrong with the numbers.

At one level, of course, it's possible to challenge the 8 million figure itself. As anybody following the story has heard repeatedly, the number includes a decent number of people who haven't paid their premiums and aren't covered. It also includes a number of people who signed up through the exchange only because the health care law took away their previous insurance.

Still, no matter what the final numbers show, at least a few million more people have health insurance now than they did a year ago.

The president's triumphal tone suggests that this is self-evidently good news and reason to celebrate the success of his health care law. He says that candidates from his party should be proud of the law and defend it. But that's not likely to happen, and the reasons are deeper than disputes about how many people actually signed up through a health care exchange.

The first is that many people are finding out that the insurance they bought through an exchange doesn't really ensure they'll get medical care. There have been repeated stories of people finding out that even though they have insurance, they can't find a doctor who will accept it. The Wall Street Journal, for example, reports that residents of New Hampshire's capital city "have to drive to other cities to get covered hospital care." Buying a product that doesn't work is a sure way to create an angry customer.

Additionally, the health care law has created even more angry customers who have found out that they have to change doctors. For some, that's just a minor inconvenience. For others, it's a huge problem.

And, of course, the law is making health insurance more expensive. The head of Aetna, Mark Bertolini, and other industry executives have said they expect to see significant price hikes from the law. That impacts tens of millions of Americans -- including many who were happy with their insurance before Obama's law was passed.

What all of this means is that the president's claim of 8 million enrollees is not something to be dismissed or ignored. But the claim's incomplete and a bit like saying a baseball score is eight. Eight runs in a major league baseball game is a good thing, but you can't really evaluate it unless you know how many runs the other team scored.

And, for the president's health care law, the negatives are still piling up a lot faster than the positives.