Boston has never elected a Black mayor. A quiet experiment could change that.

By David Scharfenberg Globe Staff,Updated January 26, 2023, 3:00 a.m.

The chain link fence was rusty and a couple of spent fluorescent light tubes poked out of the weeds.

But Andrea Campbell, a city councilor running an upstart campaign for mayor in the summer of 2021, saw potential in this vacant lot on Blue Hill Avenue — and hundreds like it scattered across Black Boston.

Housing could sprout in these places. Business ventures, too.

“This is an opportunity for us to make sure that every single neighborhood in the city of Boston is included in this prosperity that we’re seeing,” she told a gaggle of journalists and supporters gathered at the lot on a warm July morning. “That no Bostonian is being displaced, that everyone feels as though this city is theirs.”

Campbell’s message of community empowerment had broad appeal in a progressive city; she’d make a solid showing in the white, wealthy precincts of Jamaica Plain and Back Bay.

But Campbell did not finish in the top two in the preliminary election in September and advance to the final election in November. She did not get what she needed: strong turnout in Black Dorchester and Roxbury and Mattapan, neighborhoods she was promising to elevate.

An analysis for Ideas by Murmuration, a nonprofit that focuses on building data-driven political and advocacy campaigns, found that roughly 30 percent of white Boston voters cast ballots in Boston’s 2021 mayoral preliminary, but only 25 percent of Black voters and 14 percent of Latino voters participated.

Even with a historically diverse field and the racial awakening that followed the murder of George Floyd, the turnout gap that has long separated white and Black Boston did not close. Campbell came up 2,970 votes shy of a second-place finish. The other two Black candidates in the race slotted in behind her.

“The gravity of that,” says Katie Prisco-Buxbaum, Campbell’s campaign manager, “it hit us.”

The post-election blues sat heavy across Black Boston.

“My community is in grief,” state representative Russell Holmes told the Globe a couple of weeks after the preliminary election.

In time, that grief lifted. A new mayor took office. Campbell jumped into the race for attorney general. And this month, she became the first woman of color sworn into statewide office.

But the big question raised by the mayoral election never went away: What would it take to boost Black turnout, to give Dorchester and Roxbury and Mattapan greater sway in a city that has given them short shrift for too long?

Well, it turns out that amid the swirl of the mayoral campaign, a local policy lab interested in boosting voter turnout in communities of color had quietly tested out a promising strategy.

The test came too late to help Campbell or the other Black candidates win the mayor’s office. But it does offer a peek into how Black political power might be unleashed in Boston in the future.

‘Make your voice heard’

Not long after the preliminary election, a group of almost 18,000 Black Boston voters received a curious campaign mailer. No pictures of glad-handing candidates. No mention of the candidates at all.

Instead, a mild scolding.

“Thank you for voting in last year’s presidential election,” it read. “But public records show you missed voting in the important election for mayor last month.”

The mailer urged the reader to “make your voice heard” in the coming final election, highlighting the issues the next mayor would tackle — “enormous inequities” in schools, the “affordability crisis” in housing, post-pandemic jobs, and “racial disparities” in policing — and including a city website and phone number for help finding voting locations.

About a third of the recipients got a follow-up text message, with a similar pitch, the day before the election.

On some level, the effort wasn’t all that novel. Putting social pressure on voters to cast ballots — often by pointing out that public records show when they miss an election — is a well-researched and, by now, relatively common tactic in American politics.

But this particular deployment was somewhat unusual.

Much of the national investment in Black voter turnout has focused on purple states like Georgia and North Carolina, where razor-thin majorities can help determine control of the White House or Senate.

There may not be much drama in Massachusetts’ vote for president. But John Griffin, an adviser with Priorities for Progress, the lab behind the mailer-and-text campaign, says there is important work to be done here, too.

Democratic primaries for governor and attorney general, and mayoral elections in cities like Boston, are often tightly contested. And the outcomes can have powerful effects on hundreds of thousands of lives.

The “most important political decisions” in Massachusetts, Griffin says, “are made in these generally low-turnout elections.” And that’s where the most important interventions can be made.

So in 2021, Priorities for Progress used the two-stage nature of the Boston mayoral election to create a clever randomized control trial.

With the assistance of Murmuration, the data-driven nonprofit, the group identified roughly 35,500 Black voters in Boston who had cast ballots in the presidential election in 2020 but had skipped the preliminary mayoral election in 2021.

These were people who’d shown some propensity to vote — who’d turned out for the highest-profile contests — but needed a nudge to go local.

Half got the mailers and text messages urging them to vote. Half did not. Then, the researchers waited to see if the prompts had any effect on Black voter turnout in the final election.

Why the gap?

After the Civil War, Southern authorities used poll taxes, literacy tests, and a vicious campaign of violence and intimidation to suppress the Black vote. And for a century it worked. As late as the 1956 presidential election, self-reported Black voter turnout stood at just 35 percent nationwide.

Black activism in the early 1960s led to a surge in participation. And passage of the Voting Rights Act of 1965 pushed Black turnout even higher. By the 1968 presidential election, it was at 58 percent, and with Barack Obama on the ticket in 2012, it reached 67 percent.

But even with de jure barriers to voting removed, gaps between white and Black voter participation have persisted.

About 71 percent of white voters told the US Census they voted in the 2020 election, compared to 63 percent of Black voters. And Asian and Latino participation was even lower, at 60 and 54 percent, respectively.

There is no shortage of theories about why this disparity persists.

But Bernard Fraga, an Emory University political scientist who has conducted a comprehensive study of the racial turnout gap, finds the most common explanations lacking.

The data shows socioeconomic disparities aren’t as important as you might imagine. And Republican lawmakers’ cynical efforts to restrict ballot access in recent years — tightening voter ID laws and cutting back on early voting — don’t seem decisive, either.

“Instead,” Fraga writes in his 2018 book, “The Turnout Gap: Race, Ethnicity, and Political Inequality in a Diversifying America,” “I uncover a consistent pattern in who votes across all racial/ethnic groups, including Whites: when a group is perceived to drive election outcomes, members of that group are more likely to turn out to vote.

In the relatively small number of places in this country where the demography has shifted in favor of Black, Latino, or Asian American people, voters of color have shrunk the turnout gap with whites or even reversed it.

But in most of country, white people remain the dominant group and vote in larger numbers.

Here in Massachusetts, white people make up 80 percent of the population. And an analysis by the Democratic data firm Catalist for Ideas shows they consistently vote at higher rates.

One Catalist model found that, in 2020, white voter turnout in this state stood at 77 percent while Black voter turnout came in at 72 percent. That white-Black gap was 7 percentage points in 2018, 1 point in 2016, and 7 points in 2014. Another Catalist model showed wider white-Black gaps, of 13 to 15 points, in those same elections.

The Catalist analysis also shows that while white voters in Massachusetts turn out at higher rates than their peers in much of the country — the state usually ranks in the top 10 or 15 on this measure — Black voter turnout is middling compared to other states, with the state usually ranking from about 16th to 20th.

Individual candidates can only do so much to push back on these trends.

Prisco-Buxbaum, who managed Campbell’s mayoral campaign in 2021, says her team worked hard to turn out Black voters.

They sent volunteers to knock on neighbors’ doors and deliver the kind of personal endorsement that is so prized in politics. And they worked some of the public housing projects in a bid to draw infrequent voters to the polls.

But campaigns are short-lived and beset by competing demands.

“You have, at most for a big campaign, a year and a half to two years,” Prisco-Buxbaum says. “For most local campaigns, like a mayoral, you have a couple months to build an infrastructure, raise the money, and to get out the vote to win.”

Growing turnout in a sustainable way, she says, will take a lot of painstaking, trust-building, community-based organizing that transcends any single election.

Massachusetts Voter Table, a nonprofit that aims to build political power in communities of color, does some of that work. But executive director Shanique Spalding says it’s difficult to do at scale.

Her organization partners with grassroots groups that “want to get their communities — their Black communities — fired up about election cycles.” But convincing national — and even local — donors to fund long-term voter engagement programs in deep-blue Massachusetts is a challenge.

“We’re not a swing state,” she says. There is no red tide to push back.

A little here, a little there

That means clever, low-cost work at the margins — like the intervention tested out by Priorities for Progress — may be the best option here.

After the returns for the final mayoral election came in, with Michelle Wu claiming a big victory over Annissa Essaibi George, researchers took a close look at the Black voters they’d been tracking. And their best estimate was that the social pressure campaign of mailers and text messages had increased turnout by about 1.4 percentage points.

That’s a modest figure, but it’s statistically significant. And the strategy was cost-effective.

For every $1,000 invested, the experiment yielded 14 new votes. Murmuration, the nonprofit data outfit that worked with Priorities for Progress on the trial, estimates that traditional get-out-the-vote mailers, with positive encouragement to vote rather than a scolding message, yield about 10 votes per $1,000. And non-social-pressure texting turns out 7 to 10 votes per $1,000.

Griffin, the Priorities for Progress adviser, says the potential is significant.

There is a big universe of voters who turn out for presidential races but skip mayoral contests; the drop-off between the 2020 and 2021 elections was 63 percent for all Boston voters. And his group only reached out to a portion of them.

“If you have a bunch of different organizations that are running different messaging campaigns like the one that we did — it could be targeted to different specific groups of those voters, testing out different messages, testing out different delivery methods, like mail versus texting versus an email — you can have an aggregate effect,” he says.

Put it all together and maybe Black and Latino voter turnout ticks up by three or four or five points. Maybe in the next big preliminary mayoral election, a figure like Andrea Campbell makes the final and changes the face of power in Boston.

Maybe that makes a difference for the neighborhoods that haven’t shared in Boston’s prosperity.

The lot Campbell featured in her campaign event in the summer of 2021 still sits empty. A few empty beer bottles are burrowed in the dirt now. The Blue Hill Avenue traffic whistles by. And a weathered, discarded door lays on the scraggly turf, unopened.