A new political war over masks is already deepening the national divides that slowed vaccinations and thwarted what once seemed an imminent victory over Covid

The showdown not only augured a new struggle between science and politics — a disconnect that has plagued efforts to beat the worst public health crisis in 100 years. It also unleashed a face-off with extra partisan dimensions since it could preview a possible 2024 presidential election duel between DeSantis and Biden.

The latest GOP attacks were deeply ironic. Had more Republican leaders prioritized public health over politics and urged their voters to get vaccinated, the surge in new cases would likely have been avoided — meaning no reintroduction of measures to stem an again-accelerating pandemic.

Only two months ago, the CDC said vaccinated people didn’t have to wear masks indoors with the pandemic apparently in retreat. But on Tuesday, with the highly transmissible Delta variant raging, the top public health agency said that even vaccinated people in areas of “substantial” and “high” transmission of the coronavirus should mask up. And it said that everyone — staff, kids and visitors — should wear masks in K-12 schools when the summer break ends.

The decision was taken in the context of new data showing that vaccinated people infected with the Delta strain can play a limited role in transmission, even if their chances of getting seriously ill and dying are still very low.

The announcement that masking is back for many Americans came as a devastating blow to morale and could have significant political implications for a White House that made ending the pandemic this year its signature goal.

Waning patience with vaccine holdouts

New tensions over masks are also almost certain to exacerbate the disconnect between the White House, which is urging everyone to get life-saving vaccines, and pro-Donald Trump states, where there is deep resistance to public health precautions even as the virus exacts a disproportionate toll.

It will underscore the self-defeating reality that the people least likely to wear masks are often those most resistant to vaccines — a fact that is driving unnecessary new cases and deaths from the disease and now even restricting the lives of the vaccinated.

Political controversy is likely to ratchet up another notch on Thursday, when Biden is expected to announce that all federal employees and contractors must be vaccinated or face regular testing regimens.

The sign of a hardening White House line comes amid perceptible societal frustration among vaccinated Americans with those who refuse to get their shots. The most haunting realization after the CDC decision is that America, unlike many other areas of the world, has the means to end its pandemic — a plentiful supply of highly effective vaccines — but won’t fully utilize it.

“We would not be in this situation if we already had, now, the overwhelming proportion of the population vaccinated,” Dr. Anthony Fauci, the government’s top infectious diseases expert, told “PBS NewsHour.”

In a statement, Biden told the country he had unwelcome news but that he had promised to always level with citizens over the true state of the pandemic. He did offer reassurance that more mask-wearing and vaccinations would mean the country could forestall a full return to the nightmare of last year.

“Unlike 2020, we have both the scientific knowledge and the tools to prevent the spread of this disease. We are not going back to that,” he insisted.

Biden also said that while masking in schools would be “inconvenient” it would allow kids to be able to learn and spend time with their classmates again.

But DeSantis, who has frequently sought to spin political advantage from the pandemic, styling himself as the scourge of health guidance unpopular with conservatives, including on vaccine passports, quickly contradicted Biden’s advice.

“Governor DeSantis believes that parents know what’s best for their children; therefore, parents in Florida are empowered to make their own choices with regards to masking,” said DeSantis’ spokesperson, Christina Pushaw.

She claimed that data showed Covid-19 was not a serious risk to healthy children but that they were at risk of bacterial infections from masks and from difficulty breathing. The statement contradicts CDC evidence that shows more children have already died from the disease, 517 so far, than even in a bad influenza year. Pushaw also retweeted a Fox News story in which she insisted the new CDC schools guidance “isn’t based in science.”

Covid-19 cases are shooting up in almost every state, but Florida is seeing a stunning revival of the pandemic, accounting for nearly 1 in 4 of the new infections in the nation over the last week. DeSantis is now adopting a strategy that seems almost contradictory as he walks a political knife edge ahead of his reelection race next year: urging vaccines, unlike some other conservatives, but opposing most other kinds of countermeasures toward the disease.

DeSantis is a protege of Trump, though his rising political profile might soon get him crossways with the ex-President, who is mulling another White House run in 2024. In resisting CDC mask recommendations, DeSantis is following in well-trodden footsteps. Trump undermined masking guidelines right from the start in the knowledge that there was political advantage for him among base voters who believed him when he downplayed the pandemic. Most notoriously, Trump ripped off his mask in a self-aggrandizing photo op when returning to the White House after his bout with Covid-19 last year.

While a masking showdown with Biden runs directly against the government’s best health advice, it will likely do the Florida governor no harm as he continues to raise his political profile. A slump into an even deeper pandemic, however, could leave him more vulnerable ahead of his reelection race next year.

A new battle over schools

Across the nation, the new CDC guidance on masking in schools is likely to mean a highly charged start to the new semester that begins within days in some states. In New Jersey, for example, some parents are going to court to try to prevent the state’s Democratic governor, Phil Murphy, from taking any steps to require masks in class.

“We live in a constitutional democracy. We do not have government by doctors meeting in conference rooms at CDC and issuing press releases,” Bruce Afran, a lawyer for the parents, told CNN’s Victor Blackwell on Tuesday.

But the new political clashes over masking are dismaying doctors on the front lines of the pandemic, who are tired of people resisting health guidance.

“I am so sick of this virus filling my emergency department and those of my colleagues around the country. I am sick of watching sickness, severe illness and death,” Brown University Professor of Emergency Medicine Megan Ranney told CNN’s Jake Tapper. Ranney urged people to accept masking so that the country could get the Delta variant under control.

Another physician, Dr. Jonathan Reiner — a professor of medicine at George Washington University — openly blamed people who are resisting vaccines for the CDC having to issue new guidance on masks.

“The problem is that 80 million American adults have made a choice … not to get the vaccine, and these same people are not masking — and that is the force that is propagating the virus around the country,” Reiner said on CNN’s “Erin Burnett OutFront.”