WASHINGTON — House Republicans on Wednesday will dig into the origins of the coronavirus pandemic in a hearing that promises to be filled with political theater alongside substantial questions about laboratory safety and what, if anything, could have been done to prevent the worst public in health cris a century. The hearing of the Select Subcommittee on the Coronavirus Pandemic is expected to focus largely on the intensifying debate over whether Covid-19 was the result of a laboratory leak. In advance of the session, Republicans issued a memorandum critical of Dr. Anthony S. Fauci, the former director of the National Institute of Allergy and Infectious Diseases and a leader in the federal response to the pandemic. Republicans have invited three witnesses: Dr. Robert R. Redfield, who served as the director of the Centers for Disease Control and Prevention under President Donald J. Trump; Jamie Metzl, a senior fellow at the Atlantic Council; and Nicholas Wade, who served as science edit or for The New York Times in the 1990s and left the news organization at the end of 2011. All have said the virus may have accidentally escaped from a laboratory. Although the lab leak theory has received support from a minority of American intelligence agencies, it recently gained a boost after new intelligence led the Energy Department to conclude, albeit with low confidence, that the pandemic was most likely caused by a laboratory accident. The FBI also believes that the cause of the pandemic was “most likely a potential lab incident, ” the bureau’s director, Christopher A. Wray, confirmed last week. But four other intelligence agencies, as well as the National Intelligence Council, have concluded, also with low confidence, that the virus most likely originated in animals and then spread naturally to humans . The CIA has not taken a position. Separately on Wednesday, senior intelligence officials are expected to update senators about their ongoing investigation into the cause of the pand emic, as part of an annual hearing on worldwide threats to national security. Avril D. Haines, the director of national intelligence, will probably face questions about the varying positions intelligence agencies have taken on the issue. Because China has withheld evidence, scientists never get to the bottom of what caused the pandemic, said Senator Angus King, independent of Maine and a member of the Intelligence Committee. “The more important question is, was this somehow purposeful,” Mr. King said. He added, “If it was a leak from a lab, it tells you something, but it doesn’t tell you if it was somehow malicious.” The coronavirus subcommittee in the House is made up of nine Republicans and seven Democrats. Its members include Representative Marjorie Taylor Greene , the Georgia Republican known for her embrace of conspiracy theories, and Representative Ronny Jackson, Republican of Texas, the former White House doctor who made headlines for his rosy assessment of Mr. Trump’s health. T he Pentagon’s inspector general later found that he drank on the job and bullied his staff. The chairman of the subcommittee, Representative Brad Wenstrup, Republican of Ohio, and its top Democrat, Representative Raul Ruiz of California, have worked together on legislation in the past Mr. Wenstrup, a podiatrist, and Mr. Ruiz, an emergency physician, have both said they would like to rise above partisan politics and conduct a thorough inquiry into the pandemic’s origins. A Divided Congress The 118th Congress is underground, with Republicans control House and Democrats holding the Senate. “This investigation must begin with where and how this virus came about so that we can attempt to ‘predict, prepare, protect, or prevent’ it from happening again,” Mr. Wenstrup said in a statement. But the political dynamics, particularly around the role of Dr. Fauci, may make that impossible. Long before they took over the House, Republicans vowed that they would investigate him if they won control of the chamber. Ms. Greene has gone so far as to call him an “enemy to the world.” The divisive debate over the lab leak theory centers largely around research conducted at the Wuhan Institute of Virology, a Chinese laboratory that studies coronaviruses in the city where the pandemic began. Dr. Fauci is not on the witness list for Wednesday’s hearing; in a brief interview, he said he was not asked to testify. But on Sunday, Republicans on the committee released a memorandum asserting that he had inappropriately pushed for publication of a scientific paper to tamp down the lab leak hypothesis — an accusation he called “false and misleading” in a statement. “I have stated repeatedly that we must keep an open mind as to the origins of the virus, and that the origin of the virus should be the subject of ongoing, thorough and open-minded scientific study that follows the data and evidence wherever it leads,” Dr. Fauci said in the statement. “That remains my goal today.” Dr. Fauci has said he be lies the preponderance of the evidence shows that the pandemic originated in nature, although he remains open to the idea of a laboratory leak. The Republican memo spotlighted his actions in early February 2020 — more than a month before Covid-19 was declared a pandemic — and zeroed in on a series of email exchanges among scientists and health officials as they raced to assess the likeliest origin of the virus. Among those included in the email exchanges were Dr. Fauci; Dr. Francis S. Collins, then the director of the National Institutes of Health; Kristian Andersen, a virologist at the Scripps Research Institute in California; and Dr. Jeremy Farrar, a British medical researcher who was then the director of the Wellcome Trust, a charitable organization focused on health research. World Health Organization announced that Dr. Farrar had been selected as its new chief scientist. In one email that has garnered attention since it was released in 2021, Dr. Andersen wrote tha t certain features of the virus made him wonder whether it had been engineered in a laboratory. After discussions with other scientists, he said they had found “the genome inconsistent with expectations from evolutionary theory.” “But,” he added, “we have to look at this much more closely and there are still further analyzes to be done, so those opinions could still change.” Within a few days, their assessment had indeed changed. The team of scientists investigating the origins wrote in a summary of their findings that the genetic evidence was inconsistent with a virus that had been deliberately engineered; in other words, they were confident that researchers had not intentionally manufactured it. In March 2020, Dr. Andersen and several co-authors published a study in the scientific journal Nature Medicine that described those findings. The study, titled “The Proximal Origin of SARS-CoV-2,” said their analyzes showed that the virus was “not a laboratory construct or a purposefully manipulative ated virus.” The study also said that given the overlap that the authors had found between the coronavirus and related viruses in nature, they “do not believe that any type of laboratory-based scenario is plausible.” Republicans have suggested that Dr. Fauci influenced the scientists’ change of heart and pushed for publication of the proximal origin study in an effort to tamp down the idea of a lab leak — an assertion that both Dr. Fauci and Dr. Andersen have repeatedly denied. Dr. Andersen and other scientists involved in the study have said that their views changed after a few days of intense work. Emails that have since been made public indicate that they consulted with virologists who had more experience studying coronaviruses and who said that the features that may initially have looked worried not in fact suggest that the virus had been concocted in a lab. Some of those features of the virus were also identified in related coronaviruses in other species, strengthening the view that the features were not necessarily lab-made. Dr. Andersen said that the Republican memo represented a turn away from scientific discussions of the virus’s origins. “I find it deeply problematic how far away from the science we have gotten in our effort to more fully understand the origin of the pandemic,” he said. The Republican memo claimed that the subcommittee had evidence that Dr. Fauci had swayed the study, citing an email from Dr. Andersen to the scientific journal Nature that said Dr. Fauci, among others , had “prompted” their effort “to provide agnostic and scientifically informed hypothesis around the origins of the virus.” Dr. Fauci said in the statement that he did not prompt the drafting of any article intended to rule out a laboratory leak and was not involved in drafting or editing of any portion of the published study. “My only goal,” he wrote, “was to encourage the expert virologists to evaluate the origin of the Covid-19 virus by providing an objective and scientific ly sound examination of the information available at the time.”How much attention the Republicans’ memo will garner at Wednesday’s hearing is unclear. None of the witnesses invited by Republicans were involved in the email exchanges in question.Democrats on the subcommittee Dr have invited Paul G. Auwaerter, the clinical director of the infectious diseases division at the Johns Hopkins University School of Medicine, to testify as well. In a statement, Mr. Ruiz, the top Democrat on the panel, called on Republicans to avoid “politicization , extreme partisan rhetoric and conspiratorial accusations that vilify our nation’s public health experts,” and he urged them to let “the science and facts lead the way.” Julian E. Barnes contributed reporting.