(CNN) - During a stop last month in South Carolina, his first in the key primary state since announcing his bid for president, Sen. Cory Booker urgently wanted to talk about public schools.
He was in one, first of all -- sitting on a stage in the Fairfield Central High School cafeteria, in Winnsboro. But Booker also kicked off the forum with local leaders with a rallying cry around support for public education.
"I'm one of those folks who is really worrying that public education is moving backwards now and under assault, and being starved of resources," said the New Jersey politician, "and that now the kind of education you get often depends on your zip code or how wealthy your family is."
The setting and Booker's remarks stood out given his past advocacy for school choice and public charter schools -- longtime third rails in Democratic politics due to the influence of teachers unions that oppose them. Now, these forces stand to complicate Booker's chances in the primary.
Booker is not renouncing his history as a cheerleader for those policies, a central part of his story as mayor of Newark, New Jersey. But he isn't exactly highlighting it, either -- reflecting the highly charged politics around education.
Booker "is kind of caught between a rock and a hard place right now," said Jon Valant, an education fellow at the Brookings Institution. "In the race to claim the mantle of progressive Democrat, it is not helpful to be ID'ed as a supporter of school choice reforms."
But Booker "has been the Democratic darling of the charter school movement for a decade," Valant added. "If he starts to distance himself from charter schools and school choice reforms, he would be essentially distancing himself from his record in Newark."
Booker attempted to walk that political tightrope Wednesday in a CNN town hall in Orangeburg, South Carolina, where he was questioned about his support for charter schools and school choice, as well as his past association with Education Secretary Betsy DeVos.
"I fought for excellent schools no matter, whether they were magnet schools, charter schools," Booker said, maneuvering away from any mention of DeVos. "In fact, I fought to close low-performing charter schools ... We created schools that worked."
Pressed by CNN's Don Lemon about whether charter schools operate at the expense of traditional public schools, however, Booker offered that some "charter school laws ... are written in ways that really do hurt public education."
Booker added, "Local leaders need to find the best solutions for public education that work for them."
'Tarred and feathered' over charter schools
On the day before Booker launched his campaign, former New Jersey Gov. Chris Christie, who teamed up with Booker to push for and implement changes to the education system in Newark, seemed to wink at the thorny politics Booker stood to face on education -- praising his "friend" as "someone who was pro-voucher, he was pro-charter school."
"If he stays in that lane, and is the articulate, inspirational guy that he is," Christie added slyly, "then I think he's got a legitimate chance to be a serious potential problem for (President Donald Trump) in the general election."
Two months later, education policy is already playing a prominent role in the Democratic primary. This week, California Sen. Kamala Harris unveiled as her first major campaign policy proposal a plan to increase teacher pay across the country, spending $315 billion over 10 years.
Booker is acutely aware of the political minefield he must navigate over education. At a Democrats for Education Reform event held around the party's 2008 national convention, Booker recounted being "literally tarred and feathered" when he "talked about school choice."
"I was literally brought into a broom closet by a union and told I would never win office if I kept talking about charters," Booker said.
It speaks volumes then that, the week of his campaign launch, Booker reached out to Randi Weingarten, president of the American Federation of Teachers, the second largest teachers union in the country.
"We have promised that we will talk to each other," Weingarten told CNN regarding their conversation.
Weingarten and Booker have "butted heads at times, worked together at times," she said -- dating back to when Booker was mayor and Weingarten was president of the United Federation of Teachers across the river in New York City.
But, Weingarten added, "I think we have more respect for each other today than we did when he was mayor of Newark." Notably, she is reserving judgment on his presidential campaign, explaining, "Past is prologue, but prologue is the beginning, not the end."
"Instead of saying that what his positions have been before should disqualify him, let's see how he answers these questions and what he does as he's running for office," Weingarten said. "If he is where he was years ago, then it will be a problem."
'He did everything possible to destroy the public schools'
Public education is central to the story Booker is telling Democratic voters about himself and what he envisions for the country. In his campaign launch video, Booker describes his family's struggle to move "into a neighborhood with great public schools," where "realtors wouldn't sell us a home because of the color of our skin."
"As the product of great New Jersey public schools, Cory is driven to help every kid have the same opportunity he did to get an outstanding public education," campaign spokesman Jeff Giertz said.
Some detractors believe Booker's focus on public schools is the stuff of revisionist history. John Abeigon, president of the Newark Teachers Union, literally laughed at the idea that Booker would be a champion for public schools as president.
"That's priceless," Abeigon said, catching his breath. "During his tenure in Newark, he did everything possible to destroy the public schools. Hasn't done anything to help them since."
"It's sad and disappointing, because I'm a Newarker born and raised, but God help the traditional public schools in this country if he becomes president," Abeigon added.
As Newark mayor, Booker spearheaded ambitious policies that cut against the partisan grain -- by pushing to close underperforming schools, expand successful public charter schools, tie teacher pay to performance and implement a universal enrollment system.
Such seismic changes to the status quo were bound to be controversial -- and some of Booker's advisers initially counseled him against taking on changes to the education system, said Chris Cerf, a former state Education Commissioner, and later, Newark schools superintendent.
But Booker ultimately wasn't fazed by the possible political backlash, Cerf said. "Cory looked at this and said we can't be anything other than brave."
In a September 2010 interview with Oprah, Facebook founder Mark Zuckerberg said he planned to donate $100 million to support Christie's and Booker's efforts to "turn Newark into a symbol of educational excellence for the whole nation." Christie touted the opportunity to create a "national model" for education.
Today, Booker downplays that branding -- stressing that the policies he pushed were a unique solution to a unique problem, not necessarily a template for his education agenda as president.
Unlike in Newark, charter schools represent only a small fraction of public schools across the country, Booker told CNN last month. "I'm running for president of the United States," he added. "My goal is to make sure that every child and every kid has a great public school to go to."
Data shows progress in Newark
The story of Booker's education intervention is a positive one in many respects, but complicated. As Booker conceded in an interview last fall with education policy website The 74, "I've never seen such a disconnect between a popular understanding and the data."
Much of the popular understanding has been shaped by "The Prize," the 2015 book by Dale Russakoff, a veteran education reporter. The book presents a portrait of deeply flawed and disruptive policies, implemented in a top-down fashion without buy-in from the community.
"Certainly the perception since then has been that the reforms were a failure, and that there were limited to no gains," said Jesse Margolis, a founder and partner of MarGrady Research, an education consulting firm.
Margolis has analyzed data on Newark public school enrollment and student test scores from 2006, well before the policies were conceived, through 2018. Consistent with the framing in "The Prize," Margolis observed a period of disruption following the initial changes, reflected in a dip in student achievement.
But since 2014, the numbers have told a different story, with all Newark public school students showing significant gains in achievement relative to districts with comparable socioeconomic conditions. Newark charter school students, in particular, now score on average relative to the entire state.
"This data is sufficient to put to rest the argument that Newark is doing no better now than 10 years ago," Margolis said.
Margolis' findings are echoed by a 2017 Harvard study, which looked at students in grades four through eight, starting two years before the policy changes, in 2009, through the 2015-16 school year. The Harvard analysis found that the biggest driver of student achievement growth was one of the most controversial elements of the policy rollout: closing underperforming public schools and shifting students to higher-performing public schools, primarily public charters.
"I would call it a success," Thomas Kane, one of the Harvard professors who conducted the study, said of the changes made in Newark. "Some folks in Newark might not call it a success. But I would call it a success that students did shift toward schools with faster achievement growth. There were more kids in more effective schools."
Booker says 'one-size-fits-all' doesn't work
In Mason City, Iowa, last month, at Booker's first stop in the state following his campaign launch, a woman named Norma Everest started off with praise for Booker on education, saying, "I appreciate the turnaround of Newark's failing school system with charter schools."
"But I ask about your commitment to work for excellent public education to include all children of racial and socioeconomic lines and disabilities," Everest continued, "as opposed to (Education Secretary) Betsy DeVos, who knows little about public education and wants vouchers to separate wealthy and poor."
Booker responded with a plug for locally-driven policymaking: "One-size-fits-all we know doesn't work for everybody. The federal government shouldn't be telling local folks what to do."
As he unspooled the rest of his answer, however, Booker delicately avoided acknowledging DeVos, a former policy ally and now a possible albatross around his neck. Both Booker and DeVos previously sat on the board of the Alliance for School Choice; the group was an earlier iteration of the American Federation for Children, which DeVos chaired.
Forging such unorthodox partnerships has been a hallmark of Booker's approach not only to education policy, but politics more broadly.
In 2000, as a Newark City Councilman, Booker delivered a speech to the Manhattan Institute, a conservative think tank, in which he praised charter schools, school choice and vouchers.
The remarks made Booker "a pariah in Democratic circles for taking on thepParty orthodoxy on education," he told Russakoff in a 2014 interview. He also became an attraction for "all these Republican donors and donors from outside Newark," he said, "many of them motivated because we have an African-American urban Democrat telling the truth about education."
Then Booker teamed up with Christie. Oprah marveled during their education policy rollout that the two men were "putting politics aside" to help turn around Newark's failing schools.
Even as a senator, Booker has found common purpose with Republicans on education policy -- including former House Speaker John Boehner, who, along with Booker, backed vouchers for Washington, DC, schools.
After Booker opposed DeVos for Education Secretary in 2017, however, some wondered whether he was turning over a new, more partisan leaf in preparation for a presidential campaign.
"I haven't changed one iota," Booker told CNN's Jake Tapper at the time.
Booker was even more blunt in a response to New Jersey newspaper Star-Ledger: "Politics be damned. It's about doing the right thing."
Evolving on education policy
Evolving on education policy is something of a rite of passage for Democrats running for president -- from John Kerry, to Barack Obama, to Hillary Clinton. Some 2020 Democrats are already well into the process of overhauling their stances.
Take Sen. Elizabeth Warren.
In her 2003 book "The Two Income Trap," co-written with her daughter, Amelia Warren Tyagi, Warren touted public school vouchers as a system that would empower parents.
"Ultimately, an all-voucher system would diminish the distinction between public and private schools, as parents were able to exert more direct control over their children's schools," Warren wrote. "... An all-voucher system might be a shock to the educational system, but that shakeout might be just what the system needs."
More recently, however, Warren has shifted her position; in 2016, she opposed a Massachusetts effort to raise the cap on charter schools in the state.
Booker might be sanding off the rough edges of his rhetoric around education policy. Over the past few years, he has shifted focus to supporting measures compatible with the traditional Democratic Party line, including the STRIVE Act, a proposal to forgive student loans for teachers and increase funding for teacher training.
But he does not appear poised for a wholesale overhaul, even in the face of stiff political headwinds.
"He'll have to negotiate that," Cerf said. "But I know what he believes in, and I've seen him take the heat and stick to his beliefs."
Booker might not be alone in approaching education policy differently in this primary. Sen. Michael Bennet, who as Denver schools superintendent previously oversaw changes similar to those in Newark, is currently testing the waters for a presidential bid.
Meanwhile, there could be opportunity to persuade Democratic voters, many of whom have not formed a strong opinion on these issues, Valant said.
"If there's someone who's going to be able to articulate the case for charters and reforms in Newark successfully," he added, "it's going to be Cory Booker."