In Virginia, a Republican gubernatorial candidate is running ads with a three-word plan: “Open the schools.”

Outside Philadelphia, billboards warn that Democrats “blocked efforts to safely reopen schools.”

And in Florida, Gov. Ron DeSantis (R) has attacked Democrats for “putting politics and special interests ahead of what the evidence and observed experience says.”

Amid bitter fights over the role Donald Trump should play in their party, the GOP is unified behind a clear message: Restrictions on in-person learning should end, and only Republicans are ready to end them. In interviews and in ads, Republicans are hitting the talking point hard, using the issue to woo suburban voters alienated by Trump’s abrasive style.

To make their case, the GOP is using Democrats’ promise to follow the science against them. Republicans have armed themselves with research from the Centers for Disease Control and Prevention, saying that Democrats are ignoring data to keep students at home, and that only union pressure can explain why.

“These kids have been out of school in parts of this country for almost a year, and if you follow that CDC guidance, they will not go back in this school year,” DeSantis said. “That is a disgrace, that is not science. That is putting politics ahead of what’s right for kids.”

DeSantis was referring to a CDC study that found virus transmission in classrooms with masking requirements was minimal, linked to just 3.7 percent of cases in the wider community. Within 48 hours of the report’s release, the National Republican Congressional Committee claimed that Democrats were “ignoring the science when it comes to putting children back in school,” linking it to $4.2 million spent by the unions to defeat Trump.

“It’s the teachers unions that want to keep the schools closed,” Rep. Tom Emmer, the Minnesota Republican who leads the NRCC, told NBC News. Democrats, he argued, were “standing with their special-interest donors instead of the students.”

Unions that tangled with states over the initial push to reopen have consistently demanded that educators receive vaccinations as they return to the classroom. The California Teachers Association is airing ads emphasizing that their members want to “reopen schools” while “putting safety first.”

And labor leaders have accused Republicans of diverting from the pandemic by attacking a favorite target. “They’re now making hay of a problem that Trump made incalculably worse,” said Randi Weingarten, the president of the American Federation of Teachers and a member of the Democratic National Committee. “They did nothing to help us get the guidance, the data, or the resources we’d been fighting for since March of last year.”

Democrats, like the unions, say they are following the science by urging reopening only if schools can put in place significant safety measures, including masking and social distancing.

The White House, which doesn’t have individual power over the decisions of school districts, has used the issue to argue for the passage of President Biden’s rescue package, which includes billions of dollars for reopening schools.

“The president is committed to reopening schools five days a week as quickly as possible. He is committed to also following science and working with school districts . . . to get that done,” White House press secretary Jen Psaki said Thursday.

Last year, as suburban moderates bolted from Trump, Republicans struggled to find an issue to bring them back, from the threat of “socialism” to images of police overhaul protests growing into riots.

None of it was as potent as Biden’s promise to fight the coronavirus — and to get children back into schools.

At the Democratic National Convention, first lady Jill Biden, a professor, spoke from an empty classroom about “parents juggling work while they support their children’s learning” and worrying “that their kids might get sick from school.” Two weeks later, in a speech about school closures, Biden blamed Trump for the closures.

“If President Trump and his administration had done their jobs early on with this crisis, America’s schools would be open and they’d be open safely,” Biden said. “Mr. President, that’s your job. That’s what you should be focused on now. Getting our kids back to school safely.”

But restoring five-day, in-person public school across the country has emerged as one of the administration’s biggest challenges — a drama playing out across 13,506 school districts, during the largest mass vaccination campaign in American history. And the White House has struggled to lay out a clear plan.

Soon after he was elected, Biden promised that the “majority of our schools” would be open by the end of his first 100 days. On Feb. 9, Psaki said that opening “more than 50 percent” of schools for “at least one day a week” would fulfill Biden’s promise from December.

A week later, at a town hall sponsored by CNN, the president described his goal differently. “I said opening the majority of schools in K through eighth grade, because they’re the easiest to open, the most needed to be open in terms of the impact on children and families having to stay at home,” Biden told moderator Anderson Cooper.

Biden has also promised that the CDC will lay out guidelines for how schools can open safely. But its most recent guidance, released last week, recommends full in-person schooling only when levels of community transmission are quite low, a standard that almost no place in the United States meets today.

The guidance was more cautious than some were expecting, given research released by the CDC in late January, which found scant transmission of the coronavirus in schools, particularly when masks and distancing are employed. Researchers say part-time school allows for distancing and is what’s called for now, particularly given the recent emergence of more transmissible variants of the coronavirus.

Republicans have been quick to pounce on these inconsistencies.

“As the science dictates, in-person learning can be done safely with the right precautions in place,” said Rep. Ashley Hinson (Iowa), a freshman Republican whose Reopen Schools Act would require schools to have a plan to reopen to get full relief funding. “It is shocking that this issue has become so partisan and politicized — we are talking about our kids’ education and mental health.”

Republican brio has not yet been matched by public outrage. Polling since Biden took office has found that the administration’s approach to schools is less popular than other aspects of its pandemic response, but not unpopular.

A poll released Wednesday by Quinnipiac University found Americans approve of Biden’s overall coronavirus strategy by 26 points but support the schools strategy by four points, with 1 in 5 adults offering no opinion.

On Tuesday, Wisconsin voters went to the polls for a nonpartisan primary to pick their state school superintendent; a union-backed candidate got the most votes for the nonpartisan office, with most of the vote going to other liberals, and 26 percent going to a Republican-backed candidate who wants to prioritize in-person schooling for younger students.

National Republicans stayed out of that race but have been working to turn this year’s gubernatorial contests and next year’s House races into open-schools referendums. The American Action Network, a group aligned with House Republicans, has been running ads in 10 Democratic-held districts, accusing the incumbents of opposing the Reopen Schools Act because of their donations from teachers unions.

“Obviously, this right-wing group thinks Northeastern Pennsylvanians are ignorant,” said Rep. Matthew Cartwright (Pa.), one of the Democrats targeted by the ads who noted that some schools in his district were already back to in-person classes. “I’d encourage any Republicans who share this goal to leave off with the phony messaging and join us in getting this done.”

The potency of this issue may change in coming weeks. Many school districts are beginning to reopen, though mostly in a part-time way, consistent with CDC guidelines and allowing for distance inside schools between people.

A key political question may be whether voters see partially open districts as safe and well-reasoned approaches, or as failures because they do not provide full-time, traditional school.

The GOP seems to be betting on the latter. In Virginia, where Republicans haven’t won a statewide race since 2009, the party’s gubernatorial hopefuls have seized on the schools issue, with candidates from pro-Trump and more moderate wings of the party singing from the same hymnal.

“A year of learning lost, even though the data and the CDC say it’s safe to get our children back in the classroom,” said candidate Pete Snyder in one ad. “Open the schools now.”