In the hours since President Joe Biden announced his sweeping new COVID-19 vaccine requirements, the plan has been met with divergent responses, ranging from outrage and criticism to support and relief, as leaders from both the private and public sectors begin to grapple with what the new policies could mean for them.

Republican lawmakers were the most immediate and vocal opponents of Biden’s plan, arguing that he is overstepping his constitutional authority. Many threatened to challenge the new vaccine requirements in court.

“The American Dream has turned into a nightmare under President Biden and the radical Democrats,” Gov. Henry McMaster, R-S.C., said on Twitter on Thursday. “They have declared war against capitalism, thumbed their noses at the Constitution, and empowered our enemies abroad. … Rest assured, we will fight them to the gates of hell to protect the liberty and livelihood of every South Carolinian.”

Among Biden's directives is a forthcoming requirement for private companies with 100 employees or more to ensure all their workers are fully vaccinated or that they produce a negative COVID test weekly, at a minimum. He's also ordering a vaccine mandate for federal employees without a testing option.

Republican Gov. Brian Kemp of Georgia vowed to “pursue every legal option available to the state of Georgia to stop this blatantly unlawful overreach by the Biden administration.”

“The vaccine itself is life-saving, but this unconstitutional move is terrifying,” tweeted Mississippi Republican Gov. Tate Reeves.

Texas Gov. Greg Abbott also took to Twitter, calling the actions an “assault on private businesses.”

“I issued an Executive Order protecting Texans’ right to choose whether they get the COVID vaccine & added it to the special session agenda,” Abbott said. “Texas is already working to halt this power grab.”

He was joined in opposition by Texas Attorney General Ken Paxton, who just last month appeared before the Texas Supreme Court in a temporarily failed attempt to ban school mask mandates.

"President Biden continues to undermine confidence in safe and effective vaccines," said Rep. Cathy McMorris Rodgers, R-Wash. "He is using fear, control, and mandates. The pandemic will never end if American people aren’t trusted or given the information they need to assess risks and make the best decisions for themselves and their families.”

Rodgers serves as the top GOP lawmaker on the House Energy and Commerce Committee, which is tasked with overseeing health policy. 

Wisconsin Sen. Ron Johnson, a well-known vaccine skeptic, said Biden’s policy is “a level of coercion that I find highly disturbing.”

Rep. Dan Crenshaw, R-Texas, also blasted the plan:

Asked Friday about potential legal maneuvering by Republicans to stop the enforcement of the new vaccine mandates, the president shot back, “Have at it.”

"Look, I am so disappointed that, particularly some of the Republican governors have been so cavalier with the health of these kids, so cavalier with the health of their communities," Biden said during a visit to a Washington, D.C., middle school.

"We're playing for real here. This isn't a game."

Biden’s new plan comes as the U.S. continues to struggle in its fight against COVID-19, amid a resurgence of new cases fueled by the highly contagious delta variant. New COVID-19 infections in the U.S. has spiked to more than 150,000 a day, according to a seven-day average from Johns Hopkins University, and at the end of August, the U.S. was averaging more than 1,000 COVID-19 deaths a day for the first time since spring.

The U.S. did see an uptick in vaccination rates this summer as the delta variant began to ravage its way across the country, overwhelming hospitals in low-vaccinated states, many of which were treating a record-high number of young and otherwise healthy patients.

Well-known vaccine skeptics were hospitalized after contracting COVID-19. Many were chastened by their experience and walked back their earlier remarks. Some did not survive.

Still, holdouts remain, and a persistent number of Americans continue to tell pollsters they have “no intention” of ever receiving the vaccine.

Frank Luntz, a longtime GOP pollster who has held focus groups and worked with the Biden administration to combat vaccine skepticism said that, without further measures, the U.S. is likely to see vaccination rates peter off at about 75%.

 “The only way to exceed that, which he needs to for herd immunity, is to mandate it,” Luntz told the Associated Press. “It will make a lot of people angry and even more resistant, but those who are simply hesitant will act now.” Of Biden’s handling of the virus, Luntz said, “He’s done the best he can under the circumstances.”

Speaking at the White House on Thursday, Biden sharply criticized the tens of millions of Americans who are not yet vaccinated despite months of availability and federal incentives.

“We’ve been patient. But our patience is wearing thin, and your refusal has cost all of us,” Biden said, adding that the unvaccinated minority “can cause a lot of damage, and they are.”

The White House estimates its new plan will affect roughly 80 million U.S. workers. Businesses that ignore the new rules could be slapped with penalties of up to $14,000 per violation. In addition, Biden also moved to double federal fines for airline passengers who refuse to wear masks on planes or maintain face covering requirements on federal property.

 “I’m very much in favor of making and encouraging mandates,” the nation’s top infectious disease expert, Dr. Anthony Fauci, told The Washington Post on Thursday after Biden’s speech. “This was not just superficial stuff. This is going to have a significant impact.”

In his speech Thursday, Biden praised several major companies that have already implemented mandatory vaccine requirements for employees, a list that includes United Airlines, Disney, Tyson Foods and Fox News.

U.S. Business Roundtable President Joshua Bolten praised the plan, saying in a statement that his group “welcomes the Biden administration’s fight against COVID. America’s business leaders know how critical vaccination and testing are in defeating the pandemic.”

Amazon also publicly backed the move.

"We know vaccines, coupled with widespread and convenient testing, serve as powerful tools to help slow the spread of COVID-19 in our communities, keeping the U.S. economy open, and protecting America's workforce," Brian Huseman, Amazon's vice president of public policy, said in a statement. "We're proud to work with the Biden administration to increase access to affordable, high-quality, FDA-authorized tests, to keep us moving toward a full recovery."

General Motors stopped short of endorsing Biden’s requirements, but said in a statement that it supports vaccines.

“We are strongly encouraging our employees to get vaccinated given the broad availability of safe and highly efficacious vaccines, which data consistently show is the best way to protect yourself and those around you,” the automaker said.

The American Federation of Teachers, the second-largest teacher’s union in the U.S., was quick to praise the move.

“We stand in complete support of this plan and of the administration’s effort to protect as many people as possible,” AFT President Randi Weingarten said.

Other union leaders and employee advocate groups chose to weigh in, but struck a more cautious tone:

In a statement, National Treasury Employees Union President Tony Reardon said: "NTEU will monitor closely the implementation of this policy at the agencies where we represent employees to make sure that those with medical and religious exceptions are accommodated. … NTEU members, like American society at large, will have differing reactions to the new policy. Some employees will disagree. Others will welcome the additional security that comes with knowing that all of their coworkers are vaccinated.

Meanwhile, the American Federation of Government Employees – the largest union representing federal workers – took issue with the way the new policies were put into place.

“Changes like this should be negotiated with our bargaining units where appropriate,” said the group’s president, Everett Kelley. “Put simply, workers deserve a voice in their working conditions.”

Still, many business leaders declined to comment on the new rules, opting, at least in the short-term, to stay silent rather than weigh in on a public health issue that has grown increasingly politicized in recent months.

The Associated Press contributed to this report.