President Biden’s initial approach to the pandemic did not include widespread vaccine mandates, a policy that some advisers and public health officials wanted but that was viewed as a step too far.

Biden instead tried to persuade people hesitant to get a coronavirus vaccine, making reasoned arguments and emotional pleas to try to win them over while embracing requirements in limited circumstances.

His aides said the government’s role was to advocate for vaccinations, not mandate them, as they maintained hope that the vaccine skepticism stoked by misinformation on social media, conservative commentators and some Republican politicians would fade.

That hope was not realized.

On Thursday, Biden abandoned his initial strategy, instead embracing the growing frustration among the vaccinated with the country’s roughly 80 million unvaccinated citizens and announced a sweeping set of mandates, including compelling businesses with more than 100 workers to require vaccinations or weekly coronavirus testing.

It was an acknowledgment that his strategy was not working, with the virus continuing to rage in parts of the country, and a nod to how much it is hurting him politically, with his approval numbers sliding in recent weeks.

He also shed his hesitancy to wade directly into the rough currents of “pandemic politics” — as he calls the deep divide over how to approach the virus — triggering the kind of red-hot reaction on the right that he’s sought to avoid in the opening months of his presidency.

Within hours of Biden’s announcement, the Republican National Committee threatened a lawsuit to stop the administration from going forward with the rule requiring businesses to mandate vaccinations.

Other leading GOP voices have joined in that call, including South Dakota Gov. Kristi L. Noem, a potential 2024 presidential contender, who tweeted “see you in court.” Texas Gov. Greg Abbott (R) called the mandates “an assault on private businesses” and said the state is “already working to halt this power grab.” Both of the governors’ states have experienced recent surges in coronavirus cases.

The White House appeared to anticipate the GOP reaction.

“This is a political fight the president is happy to take on,” White House press secretary Jen Psaki said Friday. “What people elected him to do is get covid under control. And these are steps he needs to do in order to do this.”

And Biden, asked during a visit to a D.C. school about the threat of GOP lawsuits, said, “Have at it.”

But Biden’s quip belies the careful planning and deliberation that went into the decision to issue his new proposal.

“This was not our first preference. This was not our objective,” Psaki said in an interview Friday morning. “We wanted to try everything we could to give people the option to protect themselves.”

She noted that the White House initially believed more people would get vaccinated, particularly given that vaccines were developed under a Republican president who made a point of getting vaccinated himself.

More recently, she said, officials also hoped that full Food and Drug Administration approval of the two-shot Pfizer-BioNTech vaccine would entice more people to get it. “You hope, right? It was approved by the FDA weeks ago,” Psaki said. “Eighty million people are still not vaccinated.”

All the while, the delta variant has spread throughout the country, driving the seven-day average of new infections over 150,000 cases per day, according to a Washington Post tracker. That’s on par with where infections stood in early November, when Biden won the presidency on the promise that he would contain the virus — before vaccines were widespread.

“It has reached the point where we have to take steps to get more people vaccinated, or else we’re going to be in a never-ending virus,” Psaki said.

But the White House also watched over the summer as the private sector put in place mandates that appeared to work and didn’t trigger widespread instances of people quitting their jobs over the requirement.

And the White House kept a close eye on polling, with several aides pointing out that mandates have become more popular. A recent Post-ABC poll found that 52 percent of Americans support businesses requiring employees who come into work be vaccinated. That includes 79 percent of Democrats, 47 percent of independents and 33 percent of Republicans, the poll found.

Biden referenced national survey data Friday when asked about his new policies. “Look at the polling data,” Biden said. “The vast majority of the American people know we have to do these things. They’re hard but necessary, and we’re going to get them done.”

He also denounced what he sees as a knee-jerk reaction to his mandates as part of a larger problem with the country’s current political polarization.

“One of the lessons I hope our students can unlearn is that politics doesn’t have to be this way,” Biden said, referring to the children at the school he visited. “They’re growing up in an environment where they see it’s like a war, like a bitter feud.”

Despite the negative reaction among Republican leaders, strategists across the political spectrum predicted that Biden would not lose support for his decision and could gain some grudging backing from vaccinated Republicans.

“A majority of Americans will agree with him,” said pollster Frank Luntz, who has conducted focus groups on how Republicans are reacting to the pandemic.

He said that Biden made the move with care and that it was important for him to wait for the FDA to fully authorize the Pfizer vaccine, which was done late last month, before enacting mandates. Also he said the mounting deaths and infections from the delta variant has exasperated Americans, making them more open to harsher measures. And Biden’s decision to announce the mandates as school was starting is helpful since many families are again facing potential closures, he said.

“I think he’s done as good as he could have done,” Luntz said. “He waited until he had the evidence to prove that something needed to be done.”

The one problem with Biden’s timing, Luntz said, is that the decision coincides with the chaotic withdrawal from Afghanistan. “It doesn’t play as well as it could because of Afghanistan and the feeling that he’s made a lot of mistakes recently,” he said.

Still, Luntz predicted there would be more of a squabble among Republicans who are less united on how to handle the virus. “It will be a good issue for them in their primaries,” Luntz said of the GOP. “Democrats are unified, and in wanting people vaccinated Republicans are much more divided and angry with each other.”

Several Republicans blasted Biden’s decision, using rhetoric such as “authoritarian” and “lawless” to describe his plan to address the public health crisis.

But their heated rhetoric also raised questions about their views on the broader issue of vaccine requirements beyond the coronavirus. Several public institutions — such as public schools, the military and private employers — require vaccinations to combat a wide range of diseases, such as the measles and polio.

Many of Biden’s most outspoken critics declined to discuss what vaccine policies they believe are appropriate.

In a statement shared on Twitter, Rep. Elise Stefanik of New York, the House Republican Conference chair, called Biden’s vaccine mandate “unconstitutional, unlawful, and an authoritarian power grab.” When asked to elaborate on Stefanik’s views on the administration’s decision, her spokeswoman forwarded the same statement and declined to provide any additional details on Stefanik’s views on other vaccine requirements.

South Carolina Gov. Henry McMaster (R) said he was prepared to fight Biden’s Occupational Safety and Health Administration proposal to “the gates of hell to protect the liberty and livelihood of every South Carolinian.” His office didn’t respond to a request for more information about his views on whether there are instances when vaccine requirements should be put in place. The governor has encouraged residents to get vaccinated against the coronavirus but said that decision is up to them.

South Carolina, while providing exemptions, requires students to get several vaccines but not for the coronavirus, according to the state’s Department of Health and Environmental Control.

Celinda Lake, a Democratic pollster who advised Biden’s 2020 presidential campaign, acknowledged that the mandates could give Republicans a data point to build a broader narrative that they have been trying to create tying Biden to socialism and government control.

But she does not believe the socialism argument will be persuasive. “It’s the minority viewpoint,” Lake said. “Getting tough on vaccines is a way to gain swing voters.”

Lake also said that Biden stands to benefit in some way from turning the national conversation back to the pandemic rather than the withdrawal from Afghanistan or the looming threat of inflation. “Covid is still his best issue,” Lake said. “It is an area where people completely trust him. And it is an area where vaccinated America wanted him to get tougher.”

Biden has evolved significantly on mandates.

In December, during an event in Wilmington, Del., then-President-elect Biden was asked whether Americans should be required to take the vaccine. “No, I don’t think it should be mandatory,” Biden said, as he put on his mask. “I wouldn’t demand it be mandatory.”

By the summer, Biden was equivocating over whether he had authority to require vaccines. “It’s still a question whether the federal government can mandate the whole country. I don’t know that yet,” Biden said from the East Room in late July.

But some of the country’s most prominent public health officials were discussing mandates with the administration, including Ezekiel J. Emanuel, a professor of medical ethics and health policy at the University of Pennsylvania who was on Biden’s covid team during the transition.

“No one likes to mandate things,” Emanuel said. “Given their druthers, why start a battle about freedom and all of that? But I think in the end, they recognized that voluntarily we’re not going to get there.”

Biden had been more eager to back companies that individually decided to enact mandates for employees. But this approach risked creating an “uneven playing field,” Emanuel said. For example, nurses who did not want to be vaccinated could simply quit their jobs with one health-care company and move to another one without the requirements.

Still, Biden did back one initial set of requirements, ordering federal workers to either get vaccinated or wear masks at work and withholding federal funds from nursing homes that refused to mandate vaccinations for employers.

The current mandates still might not go far enough, Emanuel said.

“You might say this is ‘Phase 2,’ ” he said, adding that an initial round of tougher vaccine incentives that came in late July marked the first round. “This is going to get you something, but we’re going to need a ‘Phase 3’ almost inevitably,” Emanuel said.

Additional steps, he said, could include requiring Americans to be vaccinated if they want to travel between states on airplanes or trains or using some kind of mechanism to require children 12 to 17 to be vaccinated.

Mariana Alfaro, Felicia Sonmez and Eugene Scott contributed to this report.