In the case of lead, however, there was an additional element of blaming the victims: asserting that lead poisoning was only a problem among ignorant “Negro and Puerto Rican families” who didn’t fix up their dwellings and take care of their children.

This strategy succeeded in delaying action for decades — decades that left a literally toxic legacy in the form of millions of homes and apartments slathered in lead paint.

Lead paint was finally taken off the market in 1978, but then ideology stepped in. The Reagan administration insisted that government was always the problem, never the solution — and if science pointed to problems that needed a government solution, it was time to deny the science and bully the scientists, or at least make sure that panels helping set official policy were stuffed with industry-friendly flacks. The administration of George W. Bush did the same thing.

Which brings us back to the current political scene. What with everything else filling the airwaves, it may be hard to focus on lead poisoning, or environmental issues in general. But there’s a huge difference between the candidates, and the parties, on such issues. And it’s a difference that will matter whatever happens to Congress: A lot of environmental policy consists in deciding how to apply existing laws, so that if Hillary Clinton becomes president, she can have substantial influence even if she faces obstruction from a Republican Congress.

And the partisan divide is exactly what you would expect.

Mrs. Clinton has pledged to “remove lead from everywhere” within five years. She probably wouldn’t be able to get Congress to pay for that ambitious an agenda, but everything in her history, especially her decades-long focus on family policy, suggests that she would make a serious effort.

On the other side, Mr. Trump — oh, never mind. He rants against government regulations of all kinds, and you can imagine what his real estate friends would think about being forced to get the remaining lead out of their buildings. Now, maybe he could be persuaded by scientific evidence to do the right thing. Also, maybe he could be convinced to become a Buddhist monk, which seems about equally likely.

The point is that the divide over lead should be seen not just as important in itself but as an indicator of the broader stakes. If you believe that science should inform policy and that children should be protected from poison, well, that’s a partisan position.