It is not exactly news that there are big differences between judges chosen by Republican presidents and judges chosen by Democratic presidents. Of course the most visible differences involve constitutional law. For all the high-flown talk about the Constitution’s original meaning, the role of precedent, and the virtues and vices of the “living Constitution” (the idea that the meaning of the Constitution changes over time), the fact is that the views of Republican and Democratic appointees on questions of constitutional law tend to overlap with the views of Republican and Democratic presidents on questions of public policy.

In predictable ways, Republican judicial appointees differ from Democratic judicial appointees on all of the great constitutional questions of the day, including affirmative action, campaign finance regulation, gun control, abortion, and sex discrimination. On many issues, the positions of Republican and Democratic judicial appointees look uncomfortably close to their respective party platforms.

However fundamental, the debate over the Constitution misses a problem that may well be even more important in American life. Many of the most significant judicial decisions do not involve the Constitution at all. Most people never hear about those decisions. But they determine the fate of countless regulations, issued by federal agencies, that are indispensable to implementing important laws—including those designed to reform the health care system, promote financial stability, protect consumers, ensure clean air and water, protect civil rights, keep the food supply safe, reduce deaths from tobacco, promote energy efficiency, maintain safe workplaces, and much more.

Here as well, Republican judicial appointees differ dramatically from Democratic judicial appointees, and along predictable partisan lines. The outcome of the election will help determine the ultimate fate of these rules in court.

To understand this point, we need to step back a bit. Every year, federal agencies issue thousands of rules and regulations. The most important of these (usually about six hundred to seven hundred per year) go through the process overseen by the White House Office of Information and Regulatory Affairs (OIRA), which I was privileged to head from September 2009 to August 2012. Before their significant rules can see the light of day, all executive agencies have to submit their drafts to OIRA for approval.

In any administration, the OIRA process tends to be lengthy and painstaking. OIRA does not merely offer its own comments. It elicits the views of a wide range of departments and agencies, including the Department of Justice (on legal issues), the Department of State (on issues with a foreign policy component), the Council of Economic Advisers and the National Economic Council (on economic issues), the Office of Science and Technology Policy (on scientific issues), and many more. The rules that emerge from this process count as some of the most important work done in any administration.

For example, much of the Affordable Care Act cannot go into effect until the Department of Health and Human Services issues rules that actually implement its provisions. Governor Romney has repeatedly said that he would like to repeal the act (and to eliminate or scale back many other regulations). Among other things, recent rules (1) prevent the denial of coverage to people with preexisting health conditions; (2) eliminate annual and lifetime limits on coverage; (3) limit the percentage of premium dollars that can be used for purposes other than health care; and (4) ensure that parents can keep children on their plans until the age of twenty-six. The Obama administration has also issued rules designed:

• to increase fuel economy requirements for cars and trucks, saving consumers billions of dollars while reducing dependence on foreign oil; • to protect food safety, with one rule preventing up to 79,000 cases of salmonella every year; • to prevent hundreds of deaths and injuries on the highways, among other things by reducing the distance in which trucks are required to be able to come to a full stop; • to protect workplace safety, among other things by requiring new and clearer hazard warnings; • to ensure fair dealing and to avoid exploitation of college students, with new rules preventing abuses by for-profit colleges; • to promote energy efficiency with new standards for refrigerators, clothes washers, clothes dryers, small motors, and more; • to reduce the health risks associated with smoking, among other things by requiring graphic health warnings on cigarette packages; • to prevent discrimination on the basis of disability and sexual orientation; • to reduce air pollution, among other things by ensuring that states are not prevented from meeting federal air quality requirements because of pollution from other states (the “cross-state air pollution rule”).

These regulations, like almost all others, can be challenged in a court, which is typically a federal court of appeals consisting of a three-judge panel. As it turns out, a lot depends on whether the panel consists of Republican or Democratic appointees.

Here is a simple way to test whether political convictions matter in legal disputes over regulations. Ask just two questions. (1) Is the regulation being challenged by industry or instead by a public interest group? (2) How many of the three judges were appointed by a Republican president and how many by a Democratic president? If you know the answers to these two questions, it turns out that you know something important about the likely outcome. Here are three facts:

When the affected industry challenges a rule, Republican appointees are significantly more likely than Democratic appointees to vote to strike down that rule. When a public interest group challenges a rule, Democratic appointees are significantly more likely than Republican appointees to vote to strike down that rule. Judges’ likely votes are greatly affected by the positions of their colleagues. Sitting with two fellow Republican appointees, a Republican appointee becomes even more likely to side with industry. Sitting with two Democratic appointees, a Democratic appointee becomes even more likely to agree with a public interest group.

Of course the law imposes constraints; judges cannot strike rules down simply because they dislike them. But there is no question that the ultimate fate of rules protecting health, safety, and the environment may ultimately depend on whether the judges on the panel were appointed by a Republican or a Democrat.

We have very recent examples. I mentioned the Environmental Protection Agency’s important cross-state air pollution rule, which is expected to prevent, each year, 13,000 to 34,000 premature deaths, 15,000 nonfatal heart attacks, 19,000 hospital and emergency room visits, and 400,000 cases of aggravated asthma. On highly technical grounds, the court of appeals for the District of Columbia Circuit invalidated that rule just this August, by a majority vote of 2–1. (You can guess the political affiliation of the president who appointed the two judges in the majority.) Also this August, a different panel of the same court invalidated the graphic health warnings for cigarettes, again by a majority vote of 2–1. (Yes, the judges in the majority were appointed by Republican presidents.)

What this evidence suggests is that many of the biggest battles of the day—over health care reform, financial reform, environmental protection, workplace safety, civil rights—will ultimately be settled in court by lower-court judges in rulings that will get little public attention. The Supreme Court has upheld the Affordable Care Act, but some of the rules that are necessary to implement it may turn out to be vulnerable. Unlike presidents, judges often stay in their jobs for decades, and any president is in a position to shift the judiciary in major ways. Of course it is true that the 2012 presidential election will help to establish the meaning of the Constitution. Perhaps equally important, it will help to establish the fate of numerous rules designed to protect public safety, health, and the environment.

This essay is drawn from a special election symposium in the November 8, 2012, issue of the New York Review of Books, which will also include contributions by K. Anthony Appiah, Russell Baker, David Bromwich, David Cole, Elizabeth Drew, Ronald Dworkin, Darryl Pinckney, Frank Rich, Jeffrey Sachs, Michael Tomasky, Steven Weinberg, and Garry Wills.