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President Biden received more contributions from teachers unions than any other candidate during the 2020 election cycle by a wide margin -- underscoring the conundrum that may be headed for the White House if those same unions continue to oppose efforts to open schools for in-person learning. 

Biden's campaign raked in just over $232,000 from teachers unions during the 2020 election cycle, according to the Center for Responsive Politics' "Open Secrets" website. The site says the National Education Association (NEA) and the American Federation of Teachers (AFT) "account for practically all" political spending from teachers unions.

The second-highest recipient was Sen. Bernie Sanders, I-Vt., who got $50,996. 

The amount of money that went directly to any one candidate, however, pales in comparison to the money teachers unions donated to liberal groups in general -- over $23.5 million from the NEA and over $14 million from the AFT. Combined, those two groups spent $43 million in political expenditures during the 2020 election cycle, according to Open Secrets. 

They both endorsed Biden for the presidency in March.

President Joe Biden speaks about the economy in the State Dinning Room of the White House, Friday, Feb. 5, 2021, in Washington. (AP Photo/Alex Brandon)

President Joe Biden speaks about the economy in the State Dinning Room of the White House, Friday, Feb. 5, 2021, in Washington. (AP Photo/Alex Brandon) (AP)

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And the unions' influence in Democratic politics doesn't stop at money -- the AFT has 1.7 million members, according to its website, while the NEA has more than 3 million members according to its site. That's well over half of Biden's popular vote margin of victory over former President Trump in November -- a hefty chunk of the electorate. According to the NEA, one out of every 39 voters lives in a household with at least one NEA member. 

This influence could set the Biden White House on a collision course with some of its most powerful political backers as the president tries to fulfill a promise he made before assuming office -- to get kids in classrooms. 

"If Congress provides the funding, we need to protect students, educators and staff. If states and cities put strong public health measures in place that we all follow, then my team will work to see that the majority of our schools can be open by the end of my first 100 days," Biden said in December. 

That priority is broadly supported, with parents and kids nationwide speaking about the mental anguish caused by isolation and remote learning -- as well as the economic costs on the parents -- and a generation of students falling behind in school. 

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But education in the U.S. is broken up into thousands of systems in individual localities, and unions are putting up firm resistance to local many governments. 

Supporters of the Chicago Teachers Union participate in a car caravan, as negotiations with Chicago Public Schools continue over a coronavirus disease (COVID-19) safety plan agreement in Chicago, Illinois, U.S., January 30, 2021. REUTERS/Eileen T. Meslar

Supporters of the Chicago Teachers Union participate in a car caravan, as negotiations with Chicago Public Schools continue over a coronavirus disease (COVID-19) safety plan agreement in Chicago, Illinois, U.S., January 30, 2021. REUTERS/Eileen T. Meslar

In one example, as Chicago and its mayor, Lori Lightfoot, aim to get students back in schools, its local teachers union is fighting hard against the city's terms. 

A statement from the Chicago Teacher's Union last week complained that the city hadn't come to an agreement on its demands of "comprehensive testing for students and staff, remote teaching for educators with family members at risk, improvements to remote learning or phased reopening tied to vaccinations."

Added the Washington Teacher's Union this week: "[I]f the District of Columbia Public Schools continues to refuse to work with us to ensure the safety of our school facilities, we must continue to discuss ways to protect our health and that of our students. That could include a strike authorization vote later this week."

Meanwhile, the Unions of the San Francisco United School District and the San Francisco Labor Council Wednesday railed against a lawsuit from the notoriously progressive city against its school district aiming to get kids back in classrooms, calling the effort "frivolous and distracting."

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One of the top demands from unions is vaccines for teachers, despite repeated comments recently from CDC Director Rochelle Walensky that schools can open without teachers being vaccinated. 

CDC Director Rochelle Walensky speaks during a news conference at the Queen Theater December 08, 2020 in Wilmington, Delaware. (Photo by Chip Somodevilla/Getty Images)

CDC Director Rochelle Walensky speaks during a news conference at the Queen Theater December 08, 2020 in Wilmington, Delaware. (Photo by Chip Somodevilla/Getty Images)

"I also want to be clear that there is increasing data to suggest that schools can safely reopen and that that safe reopening does not suggest that teachers need to be vaccinated in order to reopen safely," Walensky said earlier this week. 

"So while we are implementing the criteria of the Advisory Committee and of the state and local guidances to get vaccination across these eligible communities, I would also say that safe reopening of schools is not — that vaccination of teachers is not a prerequisite for safe reopening of schools." Walensky added. 

But White House press secretary Jen Psaki on Thursday appeared to distance the White House from Walensky's comments and has refused to say whether the administration will stand up to unions if it needs to.

Psaki said Walensky "spoke to this in her personal capacity" and that before pushing schools to reopen without vaccines the White House will wait for "final guidance to come out."

Vaccinating teachers and other school staff is an additional layer of prevention that can be added to these key mitigation measures.

— CDC spokesperson on reopening schools

Psaki, meanwhile, called a question about whether the White House would take a stand against union obstruction if negotiations continue to stall "unfair." Asked again Friday if Biden would use the "bully pulpit" to pressure unions to let kids go back to schools, Psaki said "I'm just going to reject the premise of the question."

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Teachers, Psaki said, are "the first people to tell you that being -- teaching in the classroom and being able to engage with kids in the classroom, or middle schoolers or high schoolers in the classroom, it makes their job more enjoyable, makes them more effective at what they do. The president is absolutely committed to reopening schools ... in a safe way."

Psaki reiterated that CDC guidance on reopening schools "is not officially out yet", but that Biden wants to ensure once schools do open, they stay open and don't need to shut down because of coronavirus surges. When asked if her answer was a "yes with an asterisk" -- that the president will use the "bully pulpit" against unions if he needs to -- Psaki refused to clarify. 

A CDC spokesperson, meanwhile, responded to Psaki's statement that the director spoke "in her personal capacity" on vaccines and schools in a statement to Fox News Friday.

"Dr. Walensky’s comments are based on her review of the science. Accumulating data suggest that when key mitigation measures are strictly followed, COVID-19 does not spread rapidly in schools," the spokesperson said.

White House press secretary Jen Psaki speaks during a press briefing at the White House, Wednesday, Feb. 3, 2021, in Washington. (AP Photo/Evan Vucci)

White House press secretary Jen Psaki speaks during a press briefing at the White House, Wednesday, Feb. 3, 2021, in Washington. (AP Photo/Evan Vucci)

The spokesperson added: "These measures include wearing masks, staying at least 6 feet apart, ensuring proper cleaning and ventilation of schools, and practicing good hand hygiene and respiratory etiquette. Vaccinating teachers and other school staff is an additional layer of prevention that can be added to these key mitigation measures." 

Walensky appeared in a briefing before Psaki's comments Friday, and seemed to walk back her previous comments after the White House's public pushback Thursday.

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"I want to just emphasize that our goal is to get children back to school. Schools should be the last places closed and the first place is open," Walensky said. "Our goal is to make sure and getting children back to school that we do so both with the safety of the children and the safety of the teachers as utmost and critical in making sure that that happens."

She continued: "Among the things that we need to do to make sure that schools are safe is to make sure that the community spread of this disease is down. And that means is all of our responsibility to work, to get our children back to school safely and our teachers back to school safely."

Walensky said the CDC is "actively working" on producing "official guidance" on what needs to happen for schools to open. 

Walensky said that official guidance would be out "in the week ahead."

The White House did not immediately respond to a request for comment on how the president's political relationship with unions will affect how it handles reopening schools. 

The Associated Press contributed to this report.