More than half of the money raised by Boston mayoral candidates so far comes from outside of the city, according to a GBH News review of data from the state campaign and political finance office from September 2020 to June 14, 2021.

Approximately 57 percent of the $5.1 million collective total raised by the six major candidates thus far comes from somewhere other than the city they are seeking to lead.

When counted together, the six candidates average about $487,000 dollars from beyond Boston. The bulk of the money comes from neighboring municipalities rather than out of state.

“So much about the rest of the state is so dominated by what happens in Boston that a lot of people are going to be invested in the mayoral race,” said Boston University communications professor Tammy R. Vigil, pointing to the contributions from within the state.

John Barros, Boston’s former economic development chief under now U.S. Labor Secretary Marty Walsh, is the only candidate who has raised half of his money from within Boston. Thirty-seven percent of his funding comes from other cities and towns. Barros has also raised the least money in the race.

South End State Rep. Jon Santiago has the largest portion of money from Massachusetts municipalities outside Boston. Fifty-two percent of his $675,000 comes from surrounding cities and towns.

The other four candidates fall between Barros’ 37 percent and Santiago’s 52 percent.

More data is available on the Massachusetts Office of Campaign and Political Finance data visualization tool for the Boston mayoral race.

A spokesperson said this year is the first time the agency publicized charts for a municipal election.

“We made charts for past gubernatorial elections, and the 2013 Boston mayoral race, but this is the first time we've displayed a chart this way on the front page of the website,” said Jason Tait, OCPF education and communications director in a statement. “Because 2021 is an open mayoral race in Boston, and there's obvious interest in the race, we thought it would be helpful to post the chart for the public and the media.”

Two other mayoral candidates have also qualified for the September ballot, but have miniscule funding. Neither was included in GBH News’ calculations for this story.

Robert Cappucci, 76, of East Boston ran in 2017 and received nearly 7 percent of the 55,791 votes cast. Last month, the retired Boston police officer collected $8,910 for his campaign, most of which ($6,225) was self-funded. He now has about $5,000 in the bank.

Richard A. Spagnuolo, 63, of the North End is a first-time candidate. He has not filed the appropriate paper work with the state campaign finance office.

Donors from the Newton have given the most — about $316,000 — to the candidates so far. The average total contribution from Newton donors is about $52,600.

Myra Musicant of Chestnut Hill appears to have maxed out, giving $1,000 to the Santiago and Wu campaigns. She also gave $2,000 to the Campbell campaign and $1,500 to the Janey, despite the maximum annual individual contribution to a campaign being $1,000.

Other multi-campaign donors from Newton include Dennis Kanin, a developer with New Boston Ventures and his wife, Carol. Between the two, they've spent about $4,500 on the Barros, Campbell, Santiago and Janey campaigns.

Newton is one of the state’s wealthiest communities, having a median household income of $151,068 at last Census check.

Asked about the flow of funding from her city, Newton mayor Ruthanne Fuller said she is “not surprised” the city’s “active and interested” residents care deeply about who will next lead the city of Boston.

Larry DiCara, a former Boston City Councilor and onetime mayoral candidate, agreed.

“I used to get tons of checks from Newton because there’s so many lawyers in Newton,” he said. “Most of them work here … and they have clients who have interests in the city.”

Cambridge and Quincy are also among the top municipalities giving to Boston’s mayoral field through the period GBH News reviewed, contributing about $181,000 and $110,000, respectively.

DiCara reckons the money is benign.

“Some people have those kinds of friends who are living in other places [and] out of old loyalty or friendship will give a check. I'd like to think … that most of those are altruistic contributions rather than special interest contributions,” he said.

Michael Beckel, research director for the DC-based non-profit Issue One, offered a more skeptical view of out-of-town money.

“Certainly … if a candidate is getting the majority of their money from outside of the municipality that they are trying to lead or represent, then there could be concerns about how responsive the politician is to their actual constituents,” Beckel said. “If it seems like there are big special interests from outside of an area who are having undue influence in the official policy making, that's when it can really be concerning.”

The perception of special interests invading Boston politics flared up last week as the Better Boston super PAC, which is backing City Councilor Andrea Campbell, filed its first expenditure report. The posting showed several deep-pocketed donors — some of whom are known charter school supporters.

The top three donors were Andrew Balson of Newton, Netflix CEO Reed Hastings — each chipping in $125,000 — as well as Stig Leschly, a former CEO of the Boston charter school non-profit Match Education, and former state judge Nonnie Burnes who both gave $100,000.

Much like the mayoral campaigns, a large portion — about 43 percent — of the super PAC’s money came from Massachusetts cities and towns outside Boston.

When it comes to out of state money streaming into the campaigns, about 13 percent of the candidates’ collective total comes from outside Massachusetts.

“Out of state [money] says something a lot different,” said Vigil. “While it's not uncommon for [out-of-state money to flow into] any kind of major city race … it certainly would be disturbing if it was an extraordinarily high amount of money that's coming in from outside sources.”

At-Large City Councilor Michelle Wu has the largest portion of out-of-state money in the race. About 18 percent of her total $1.2 million comes from somewhere other than Massachusetts.