WASHINGTON — Robert F. Kennedy Jr. stood earlier than the Lincoln Memorial in January 2022 and condemned the federal authorities’s coronavirus response by railing in opposition to totalitarianism. Jews in Nazi Germany, he steered, had extra freedom than Individuals going through vaccination mandates and college, church and enterprise closures within the period of Covid-19.

“Even in Hitler’s Germany, you could possibly cross the Alps to Switzerland,” he informed a crowd of flag-waving anti-vaccine lovers at a “Defeat the Mandates” rally. “You could possibly conceal in an attic like Anne Frank did.”

Mr. Kennedy later apologized, although it was not the primary time he had invoked the Holocaust. Over the previous 20 years, as he has pursued what he calls “protected vaccine activism,” Mr. Kennedy has advanced from an environmental lawyer involved about mercury poisoning right into a crusader for particular person liberty — a path that has landed him, a scion of a storied Democratic clan, within the unlikely embrace of the American political proper.

On Wednesday, Mr. Kennedy, plans to formally announce that he’s difficult President Biden for the Democratic nomination for president. His vaccine skepticism offers him one thing in widespread with one other candidate: former President Donald J. Trump, who like Mr. Kennedy has blamed childhood vaccines for autism — a discredited concept that has been repudiated by greater than a dozen peer-reviewed scientific research in a number of international locations.

“Robert F. Kennedy might leap into the Republican main for president and solely DeSantis and Trump, I feel, would do higher,” Stephen Okay. Bannon, Mr. Trump’s former chief strategist, mentioned not too long ago on his podcast, referring to Gov. Ron DeSantis of Florida. Mr. Bannon mentioned Mr. Kennedy had a “large following” together with his viewers. “Folks love this man,” he mentioned.

Vaccination is a singular public well being success that has saved untold tens of millions of lives. Vaccines have eradicated smallpox, averted tens of millions of deaths from measles and despatched naturally occurring polio instances plummeting, from an estimated 350,000 in 1988 to 6 reported instances worldwide in 2021, in keeping with the World Well being Group.

Mr. Kennedy has insisted that he’s not against vaccines and that his sole curiosity is in making them safer. “I’m not anti-vaccine, though I’m type of the poster little one for the anti-vax motion,” he mentioned throughout a latest speech at Hillsdale School, a conservative Christian faculty in Michigan.

However via his nonprofit, Kids’s Well being Protection, and his films, speeches and books — together with one which portrays Dr. Anthony S. Fauci as within the pocket of the pharmaceutical trade — Mr. Kennedy has used his platform and his household’s star energy to sow doubts about vaccine security, spreading misinformation by twisting info out of context.

In 2021, the Heart for Countering Digital Hate named him one in all its “Disinformation Dozen” — the 12 individuals whom the group discovered to have been accountable for roughly three-quarters of anti-vaccine content material on Fb.

Fb and Instagram have eliminated the accounts of Kids’s Well being Protection, and Mr. Kennedy has accused them of censorship. He’s additionally suing the Biden administration and Dr. Fauci, who for many years led the Nationwide Institute of Allergy and Infectious Ailments, accusing them of pressuring social media firms to censor free speech.

Mr. Kennedy declined to be interviewed. In an e-mail message, he mentioned Kids’s Well being Protection had “an especially strong fact-checking operation.” He additionally pointed to a response by Meta, Fb’s mother or father firm, disputing the “Disinformation Dozen” report. Meta critiqued the examine’s design, saying that specializing in simply 12 individuals “misses the forest for the bushes.”

Household Backlash

Mr. Kennedy, 69, is the third-eldest little one of Robert and Ethel Kennedy and a nephew of former President John F. Kennedy, who urged Individuals to take the Salk polio vaccine and signed the Vaccination Help Act of 1962 to assist states and cities perform childhood immunization applications.

His activism, and now his political aspirations, have been wrenching for his household. A few of his members of the family have publicly rebuked him. His sister Rory Kennedy informed CNN she was backing Mr. Biden, whereas his sister Kerry Kennedy mentioned in a press release, “I like my brother Bobby, however I don’t share or endorse his opinions on many points.”

Forward of his White Home bid, Mr. Kennedy is enjoying up his household historical past. He lives in California however plans to make his announcement in Boston, a metropolis carefully recognized with the Kennedys. He not too long ago tweeted a photo of himself in a classic “Kennedy for President” T-shirt.

His identify and household fame have opened doorways for him. Dr. Fauci mentioned he had met with Mr. Kennedy a number of occasions and had informed him “that I consider that his intentions should not evil, however his info is wrong, and he’s misguided and may inadvertently trigger vital hurt.” Dr. Fauci mentioned that when Mr. Kennedy’s ebook about him, titled “The Actual Anthony Fauci,” got here out in 2021, he was “actually shocked.”

“The complete ebook is such an entire lie,” Dr. Fauci mentioned.

Mr. Kennedy’s messages typically have a grain of fact. The Kids’s Well being Protection web site, for example, says “vaccines comprise many substances, a few of that are identified to be neurotoxic, carcinogenic and trigger autoimmunity.” Vaccines do comprise preservatives and components, comparable to aluminum salts, which have been in use in vaccines for many years. Research present antagonistic reactions are uncommon and sometimes contain pores and skin allergic reactions.

The Kids’s Well being Protection web site additionally states that sure vaccines should not examined in opposition to placebos in medical trials, citing polio, hepatitis and meningitis vaccines as examples. That’s deceptive. Model-new vaccines — from polio to measles to Covid-19 — are examined in giant medical trials that embody placebo teams. However scientists agree it will be unethical to withhold lifesaving vaccines from examine members. For that purpose, when older vaccines are reformulated or up to date, research don’t embody a placebo group.

“Vaccine accidents can and do occur,” the web site declares. That’s true as properly, however the federal authorities has an aggressive system to trace and detect unintended effects to allow them to be addressed.

The measles vaccine, for example, lowers the platelet depend in about one in each 25,000 to 30,000 individuals. That may trigger crimson spots from bleeding beneath the pores and skin — an issue that’s normally “short-lived and self-resolving,” mentioned Dr. Paul A. Offit, the director of the Vaccine Training Heart at Kids’s Hospital of Philadelphia. However measles causes that downside in a single in 3,000 youngsters — roughly 10 occasions as many because the vaccine, he mentioned.

“There aren’t any risk-free selections, simply selections to take completely different dangers,” mentioned Dr. Offit, who has been a vocal critic of Mr. Kennedy. “You could possibly argue the best threat of vaccines is driving to the workplace to get them.”

A Motion Grows

By his personal account, Mr. Kennedy was at first a reluctant critic of vaccination. He acquired concerned in 2005, when he was an environmental lawyer suing coal-fired energy vegetation to power them to cut back emissions of mercury and different poisonous chemical compounds.

The anti-vaccine motion in the US had been rising amid debate over an increase in instances of autism. In 1998, a British physician named Andrew Wakefield printed a examine of 12 youngsters in The Lancet, a prestigious medical journal, that steered a hyperlink between the measles, mumps and rubella vaccine and autism.

The article was retracted in 2010, and Mr. Wakefield was later barred from working towards drugs. However within the years after its publication, one other concept started to take maintain: that thimerosal, a mercury-based preservative that had been used for many years to forestall micro organism from rising in multiple-dose vials of vaccines, induced autism.

The measles, mumps and rubella vaccine by no means contained thimerosal, however different vaccines given to infants did. The Facilities for Illness Management and Prevention says there may be “no proof” that the low doses of thimerosal in vaccines trigger hurt, “apart from minor reactions like redness and swelling on the injection web site.”

However in 1999, after Congress directed the Meals and Drug Administration to have a look at mercury in all merchandise, the American Academy of Pediatrics, federal well being companies and vaccine producers agreed that thimerosal must be faraway from childhood vaccines. The choice was made “out of an abundance of warning,” mentioned Daniel Salmon, the director of the Institute for Vaccine Security on the Johns Hopkins Bloomberg College of Public Well being.

However the transfer alarmed dad and mom. As Mr. Kennedy traveled the nation giving speeches, he has mentioned, moms of intellectually disabled youngsters started buttonholing him, urgent him to research vaccines.

“They might say to me in a really respectful but in addition type of vaguely scolding manner, ‘In case you’re actually desirous about mercury exposures to youngsters, it’s essential take a look at vaccines,’” he informed the Hillsdale School viewers.

In 2005, Rolling Stone and Salon copublished an article by Mr. Kennedy, headlined “Lethal Immunity,” that blamed thimerosal in vaccines for fueling the rise in autism. Salon later retracted the article. Mr. Kennedy insisted Salon caved to strain from authorities regulators and the pharmaceutical trade.

Thimerosal continues to be utilized in flu vaccines. In 2015, shortly after Mr. Kennedy printed a ebook concerning the preservative, he met Eric Gladen, an engineer who believes he was sickened by thimerosal in a tetanus vaccine and who made a movie about his expertise. The 2 joined forces. Mr. Gladen’s advocacy group, World Mercury Undertaking, was later rebranded as Kids’s Well being Protection.

“We had two large instruments to boost funds; we had my movie, which is about 10 years of analysis put into 90 minutes, and his ebook,” Mr. Gladen mentioned in an interview, including, “Between him being a Kennedy, the movie and his ebook, it compelled lots of people to get entangled.”

The anti-vaccine motion was, on the time, largely the province of the political left. Mr. Kennedy discovered allies in Hollywood celebrities like Jim Carrey and Jenny McCarthy. In California, he waged an unsuccessful combat in opposition to a invoice to eradicate the “private perception” exemption that allowed dad and mom to decide out of vaccinating their youngsters.

Mr. Kennedy has been a vocal opponent of the Vaccine Damage Compensation Act, a 1986 federal legislation meant to advertise the event of vaccines by shielding producers from lawsuits. In 2003, on the peak of the thimerosal controversy, a bipartisan measure to replace the legislation by providing immunity to vaccine additive producers collapsed in Congress.

Mr. Kennedy factors to such efforts as proof that lawmakers and federal regulators are conspiring to guard drug firms, which he says lack incentives to deal with security. Throughout the combat over the California laws, he invoked these arguments, mentioned Dr. Richard Pan, a former state senator who was an writer of the invoice and met with Mr. Kennedy on the time.

“He primarily targeted on the F.D.A. being corrupt and in cahoots with the pharmaceutical firms to cover the hazard of vaccines,” Dr. Pan mentioned.

Assembly With Trump

Shortly earlier than Mr. Trump was inaugurated in January 2017, Mr. Kennedy met with him at Trump Tower in Manhattan. Mr. Kennedy mentioned afterward that the president-elect wished him to guide a “vaccine security and scientific integrity” fee. He informed Science journal that Mr. Trump had informed him he had 5 buddies whose wholesome youngsters “developed a collection of deficits” after being vaccinated.

The fee by no means got here to go, however the coronavirus pandemic gave Mr. Kennedy an excellent larger platform. Because the nation grew ever extra polarized, with a lot of Mr. Trump’s followers shunning the vaccines and Dr. Fauci changing into a lightning rod, Mr. Kennedy’s ebook about Dr. Fauci grew to become a finest vendor.

One other ebook by Mr. Kennedy is due out in June, this time specializing in the controversy over the origins of the coronavirus. Titled “The Wuhan Cowl-Up,” it claims that federal well being officers “conspired with the Chinese language navy” to cover the pandemic’s origins — an assertion that seems to conflate experiments by the Chinese language navy on the Wuhan Institute of Virology with different work there funded by the U.S. authorities.

How a lot Mr. Kennedy will discuss vaccine security throughout his presidential marketing campaign stays unclear. As he did throughout the rally on the Lincoln Memorial, he used his speak at Hillsdale School to cloak his activism in a broader level — that the federal government, the press and social media firms try to silence him, pushing the US towards tyranny.

“The founders, particularly Hamilton, Madison, Adams, mentioned, ‘We put freedom of expression within the First Modification as a result of all the opposite amendments are depending on it,’” Mr. Kennedy mentioned. “As a result of if you happen to give a authorities the proper to silence their opponents, they now have a license for any atrocity.”