WASHINGTON — For the past two years, as the coronavirus has wreaked havoc on American lives and the world at large, Dr. Ashish K. Jha has been there to make sense of it all. He has been hard to miss.

You could find him on MSNBC, before vaccines arrived, bluntly acknowledging that “it’s hard to overemphasize how bad things are.” Or on CNN, upbraiding maskless lawmakers for spreading Covid-19, or Fox News, proclaiming remote schooling “a disaster.” The Museum of Science in Boston went so far as to create a hologram of Dr. Jha last year, using artificial intelligence and sound clips, to answer coronavirus questions.

Now Dr. Jha, the dean of Brown University’s School of Public Health, a respected academic and a practicing internist with minimal government experience, is about to join the White House as President Biden’s new coronavirus response coordinator. Dr. Jha, a preternaturally calm 51-year-old whom the health news site Stat once described as “network TV’s Everyman expert on Covid,” is going to take charge of the most complicated federal response to a crisis in modern history.

While his communication skills will help, there is much more to the job than talking to the public. It requires coordinating across government agencies and the private sector, from the Food and Drug Administration, which considers which drugs and vaccines to approve, and the State Department, which works to get vaccines overseas, to drugmakers and pharmacies.

“Probably his biggest challenge is that he doesn’t know government, he doesn’t have experience, and it does take a while to know who you should call, who you can’t and how you get through the hierarchy,” said Dr. Anthony S. Fauci, Mr. Biden’s top medical adviser for the pandemic, who will work closely with Dr. Jha. “But he’s a smart guy. He’ll figure it out.”

Dr. Jha’s selection signals two things about Mr. Biden’s thinking. First, the president wants to keep the federal pandemic response centered in the White House, instead of delegating it to the Department of Health and Human Services or one of its agencies, the Centers for Disease Control and Prevention. Second, he wants to put it in the hands of a public health expert. Dr. Jha is replacing Jeffrey D. Zients, an entrepreneur and management consultant who presided over a huge mobilization of coronavirus vaccines, tests and therapeutics over the past 14 months.

With the supply and logistics infrastructure now in place, Dr. Jha will face different challenges. Virus cases are rising in parts of Europe and Asia, and most experts, including Dr. Fauci, believe the numbers will rise again here. Yet many Americans do not want to think about the pandemic anymore. Mask mandates have lifted all over the country — even the federal Department of Health and Human Services is making masks optional — and many Americans will most likely resist putting them back on, even if conditions warrant it.

“How this plays out depends on how the dynamics of Covid play out, and frankly how much time elapses before he has to tell the American people we’re in trouble as well,” Dr. Nicole Lurie, who served as assistant health secretary for preparedness and response during the Obama administration, said of Dr. Jha. “And that could plausibly happen before he steps into this role, or on Day 1.”

Dr. Jha may also get caught up in a bitter funding battle between the White House and Congress, where the administration’s request for $22.5 billion in emergency coronavirus relief aid is stalled. If no agreement is reached by the time he takes office in April, the government will be out of money to buy more therapeutics and vaccines.

With his gentle manner and professorial glasses, Dr. Jha has often been a soothing figure on television — unlike Mr. Zients, whose public speaking tends to sound stiff and scripted. Dr. Jha speaks in plain, easy-to-understand language, assuming that ordinary people “don’t want to hear a debate about the R-naught,” he told Stat, referring to a way to measure the transmissibility of a virus. They do, he said, “want to hear what the new variants mean to them, when their kids might be eligible for a vaccine.”

With that in mind, Dr. Jha could help solve what has been one of the administration’s biggest failings: its confusing messaging, which stems partly from a lack of coordination between agencies. Dr. Rochelle Walensky, the director of the C.D.C., has fumbled at times in communicating the agency’s coronavirus guidance to Americans.

And while Dr. Fauci has been the administration’s primary spokesman on the pandemic, he has become a polarizing figure and a target of frequent Republican attacks, to which he has at times responded heatedly in public and while testifying on Capitol Hill.

So far at least, Dr. Jha has been able to reach people across the political spectrum. He makes it a point to appear on conservative channels and is a regular guest on Newsmax, a favorite of former President Donald J. Trump.

“He seems like a credible guy on TV,” said Scott Jennings, a conservative commentator who is close to Senator Mitch McConnell of Kentucky, the Republican leader. (Mr. Jennings’s advice to Dr. Jha: “Don’t treat Congress the way Fauci has.”)

Public health experts are hopeful that Dr. Jha will be well positioned to tone down the divisiveness, as neither his appearances on conservative outlets like Fox News nor his active Twitter feed (over 340,000 followers) have incited much backlash so far.

“He is a deeply civil personality,” said J. Stephen Morrison, a global health expert at the Center for Strategic and International Studies who worked with Dr. Jha on a report analyzing the international response to the Ebola crisis of 2014 and 2015. “He comes across as a caring, smart, listening person who also knows how to speak across political divides in language that’s intelligible. There are not a lot of people that can do that.”

But Dr. Jha is already drawing criticism from some public health experts who believe that he has been too cozy with the Biden administration and has often echoed White House talking points. One of them, Dr. Walid F. Gellad, a health policy professor at the University of Pittsburgh, suggested on Twitter last week that certain “public health experts” who are “tweeting and writing support for administration policy 2 minutes after policy is released” should not be viewed as “objective and impartial.” Though he did not mention anyone by name, he confirmed in an interview he was referring to Dr. Jha.

People with weakened immune systems, who remain at high risk for Covid-19, worry that Dr. Jha is too eager to abandon mask mandates and other strategies that help protect them, said Janet Handal, the president of the Transplant Recipients and Immunocompromised Patient Advocacy Group.

“Dr. Jha has been a comforting voice for many; however, this is coming at the expense of the immunocompromised, whose concerns and risks he has continually minimized or discounted,” she said.

For instance, when the C.D.C. cut the isolation period for Covid-19 patients to five days from 10 days in December — a move that many public health experts criticized — Dr. Jha tweeted that it was “terrific.” And The New York Times published a guest essay from him last month in which he called the C.D.C.’s move to relax its masking guidelines “a welcome change.” The article appeared on the same day the new guidelines were announced.

Dr. Jha said through a Brown University spokeswoman, Mahrokh Irani, that none of his past statements had been coordinated with the White House, and that he had “never received specific talking points” from the administration. But, Ms. Irani added, he is on a list of experts who regularly receive “updates and announcements” from the White House communications team.

Dr. Jha’s supporters say that he will push back if he disagrees with Mr. Biden or other White House officials on pandemic strategy.

“He never held back,” said Dr. Julio Frenk, the president of the University of Miami, who worked closely with Dr. Jha when both were at Harvard’s T.H. Chan School of Public Health. “It’s obviously a very different context, but when he felt things were not going well at Harvard University, he did not hold back in expressing that.”

Dr. Jha was born in Bihar, a state in eastern India that is among the poorest in that country. When he was nine, his parents moved their family to Toronto. He showed up, he told The Providence Journal in an interview last year, “not speaking a word of English.”

The family later moved to New Jersey, where Dr. Jha was valedictorian of his class and editor in chief of the Boonton High School student newspaper. After graduating from Columbia University, he became a student at Harvard Medical School — mostly because his parents wanted him to be a doctor, though he soon decided medical school was “the coolest thing ever.”

After earning a master’s degree in public health, Dr. Jha focused his early research on improving the quality of health care systems, while he continued to practice medicine. But over time, Dr. Frenk said, he became drawn to issues related to global health, and he eventually became the director of the Harvard Global Health Institute.

While at the institute, Dr. Jha joined Dr. Peter Piot, of the London School of Hygiene and Tropical Medicine, in leading an independent examination of the international response to the Ebola outbreak in West Africa in 2014. His assessment of the World Health Organization was blistering: “The most egregious failure was by W.H.O. in the delay in sounding the alarm,” he said then.

When Dr. Jha left Harvard for Brown in September 2020, the pandemic was already underway — and in the short time since it had taken root, Dr. Jha had already become a media star. He continues to live in Newton, Mass.; Ms. Irani, the Brown spokeswoman, said he intended to move to Washington and take a leave from his job as dean.

In Washington, Dr. Jha will have to “gain the respect and trust” of people like Dr. Fauci, said Dr. Joshua M. Sharfstein, a former Food and Drug Administration official who lived with Dr. Jha when both were studying medicine. Dr. Fauci, for the record, said that he had watched Dr. Jha on TV and that “I haven’t heard him say anything that I wasn’t actually in agreement with.”

Dr. Jha will also have to chart a course through a period that could bring more tumult — and persuade Americans that it is the right one.

“He’s been able to boil things down into news that people can use, so people have really looked to him for a candid assessment,” Dr. Sharfstein said. “That obviously isn’t the whole job, but I do think it’s his superpower.”

Kitty Bennett contributed research.