Fortunately, options for fortifying the F.D.A. abound. For instance, laws that would make it easier for regulators to police the cosmetics industry and to hold medical device companies to account have been floating through Congress for years. A group of former F.D.A. commissioners last year proposed an even bolder fix: Restore the agency’s autonomy by extracting it from the Department of Health and Human Services. The F.D.A.’s decisions used to be final, but for decades now they have been subject to layers of political interference. Making the agency independent, as the Federal Reserve and the Social Security Administration are, could help reverse that trend.

But for these or other worthy ideas to get a fair hearing, Congress will have to step in, and the president — and the electorate — will need to come to terms with the essential role of regulations in protecting the nation’s food and drug supply.

In the meantime, the challenge of steering the F.D.A. will fall to Dr. Hahn. He will not have nearly enough resources to carry out the agency’s stated mission — no commissioner ever does. But he will not be completely powerless, either. Here are four things Dr. Hahn would do well to keep in mind as he takes the reins.

Stay vocal. Dr. Hahn’s predecessor, Dr. Gottlieb, managed to keep a spotlight on his chosen priorities — namely e-cigarette regulations and generic drug development — with a relentless and multifaceted public messaging campaign. He tweeted, he blogged, he gave speeches and he communicated openly and regularly with the press. Dr. Gottlieb did not achieve all of his goals — in fact his e-cigarette strategy backfired, badly. But he made the F.D.A. less opaque, and he gave the agency an urgently needed voice. Dr. Hahn will have an easier time defending the agency, and keeping it relevant, if he fosters the same transparency.

Slow down on drug and device approvals. The F.D.A. has made several compromises in recent years — such as accepting “real world” or “surrogate” evidence in lieu of traditional clinical trial data — that have enabled increasingly dubious medical products to seep into the marketplace. Dr. Hahn ought to take a fresh look at some of these shifting standards and commit to abandoning the ones that don’t work. That will almost certainly mean that the approval process slows down — and that’s O.K.

Stand up for science. As reporting from the medical news website Stat and other outlets suggests, the F.D.A. has become too susceptible to outside pressure. Regulators approved a powerful new opioid at the Department of Defense’s urging, fast-tracked a dubious antidepressant after President Trump praised it, and reversed its decision to reject a muscular dystrophy drug after patient groups complained loudly. Such kowtowing hardly inspires confidence. Scientific evidence (or the lack thereof) needs to be the deciding factor in any final regulations from the F.D.A. That means saying no to politicians and drug and device makers — as well as patients’ groups — when their demands are not supported by the agency’s own findings. It also means holding companies to account when they fail to complete postmarket studies, or when their products prove faulty or dangerous.

Follow through on existing commitments. The F.D.A. has yet to issue guidelines for the regulation of increasingly popular CBD products after promising to do so by the end of 2019. E-cigarette makers are supposed to submit their applications for market approval to the agency by May. And a regulatory grace period that the agency granted to so-called stem cell clinics back in 2017 is set to expire this year; when it does, regulators will need to figure out how to police nearly 1,000 businesses selling injections and other treatments that have not proved to work and that have already caused some patients serious harm. Dr. Hahn would build a lot of good will if he showed the F.D.A.’s critics — and the public at large — that he takes all of these deadlines seriously.