SEEKONK, Mass. (WPRI) — All but one of the Democrats running to succeed Massachusetts Congressman Joe Kennedy III are promising to release their tax returns before the Sept. 1 primary, as the nine candidates’ personal finances emerge as a bigger issue in the campaign.

Jesse Mermell, a former Brookline Select Board member seeking to establish herself as the leading progressive option in the 4th Congressional District, was the first candidate to release her tax returns, doing so back on June 18, and has posted six years’ worth to her website.

Mermell, who files as a single taxpayer, reported adjusted gross income of $153,055 for 2019, when she was working as CEO of a progressive business group. The returns shows she paid $28,299 in federal taxes.

“With Donald Trump lying, cheating, and deceiving his way through a failed presidency, Democrats have an obligation to lead by example and run open, transparent campaigns that are accountable to the voters,” Mermell campaign manager Katie Prisco-Buxbaum said in a statement.

“Voters have a right to know if corporate special interests are the real fuel behind a campaign, or about any potential conflicts of interest,” she continued. “That’s why Jesse released six years of her tax returns – documents that provide more comprehensive information than the mandatory public disclosure forms.”

While a six-figure income is nothing to sneeze it, Mermell appears to be one of the less wealthy candidates in the 4th District primary, based on a review of mandatory personal financial disclosure statements they’ve filed with the U.S. House of Representatives. Multiple candidates reported well over $1 million in assets to their names.

The only one of the nine Democrats who refused to share his tax returns when asked by WPRI 12 was Chris Zannetos, a Wellesley tech entrepreneur. Federal Election Commission filings show Zannetos has already put in $306,000 of his own money to fund his campaign.

“Federal election rules require significant financial disclosures to be filed by congressional candidates. We have filed those disclosures completely and on time, and will continue to do so,” Christen Baglaneas, a spokesperson for Zannetos, said in an email. “These rules do not require candidates to release their taxes, and Chris won’t be going beyond the federal requirements.”

Zannetos’ personal financial disclosure form lists six pages of investments, accounts and trust funds in which he has an interest, with multiple holdings valued at a minimum of $250,000. (The House only requires lawmakers and candidates to report the value of their assets in broad ranges.)

Democrats have long attacked President Trump for refusing to release his tax returns, an issue that led to a U.S. Supreme Court decision just last week. But Zannetos’ spokesperson argued there is “a fundamental difference” between a president and a member of Congress, because a president “has the vast ability to enrich himself.”

Beyond Mermell and Zannetos, the other seven candidates all expressed varying degrees of willingness to release their tax returns.

However, only one candidate — Dr. Natalia Linos, a Harvard epidemiologist who entered the race in May — has actually joined Mermell in doing so at this point. Linos’s campaign has posted her 2017 and 2018 returns on her website, and said it will soon post her 2015, 2016 and 2019 returns, as well.

Linos and her husband, Paul Hanna, reported $281,390 in adjusted gross income for 2018, paying $65,757 in federal income tax. (Hanna works for the federal government.)

Another Democratic candidate’s finances have come under the spotlight this month: Ihssane Leckey, a former financial regulator and Bernie Sanders supporter who recently stunned her opponents by dropping $650,000 of her own money into her campaign, bringing her personal investment in the race to $750,000 so far.

Leckey’s deep pockets had been unknown because she failed to file her personal financial disclosure with the House until last Friday, more than a year after she entered the primary. She and her husband, energy trader Sean Leckey, disclosed assets worth between $1.2 million and $2.9 million on the form.

“Ihssane will release her tax returns in the next few weeks,” her spokesperson, Josh Miller-Lewis, said in an email. “She is in the process of gathering the necessary documents and will release as many years as possible as quickly as she can.”

Mermell’s campaign — which faces a unique threat from Leckey as a challenger for the progressive vote — took aim at her in an email blast to supporters over the weekend, warning that Mermell’s opponents were “spending big money flooding the airwaves with TV ads – and they’re doing it by writing themselves big checks and getting backing from corporate special interests.”

Leckey is one of three candidates who has begun airing TV ads, along with Newton City Councilor Jake Auchincloss and City Year co-founder Alan Khazei. Her campaign has sought to turn her financial wherewithal into an advantage. “Based on our polling and Ihssane’s significant fundraising advantage, she is progressives’ best chance to win this race,” Miller-Lewis said last week.

Miller-Lewis also emphasized that Leckey will not accept donations from corporate PACs or lobbyists.

Auchincloss, who has posted the strongest fundraising numbers among the nine candidates, also committed to releasing his tax numbers before the primary. He and his wife Michelle, who works for Bain & Company Inc., listed nearly $350,000 in salary income for 2019 as well as significant investment and real estate assets on his disclosure form.

“Jake has been a strong advocate for transparency in campaign finance; as a city councilor he called out corporate spending in local elections,” Auchincloss spokesperson Yael Sheinfeld said. “He’s released a personal financial disclosure, and plans to release his tax returns in the near future.”

Khazei plans to release five years of tax returns, according to spokesperson Keyon Rostamnezhad.

“Alan just filed his 2019 tax returns and is working with his accountant to release his previous years,” Rostamnezhad said. “He will do so soon and well in advance of the primary on Sept. 1.”

Khazei’s personal financial disclosure showed he earned $160,000 in 2019 as a consultant for Issue One, a nonpartisan group whose mission is repairing American democracy. He and his wife Vanessa Kirsch, founder of a venture philanthropy firm called New Profit Inc., also disclosed over $1 million in investments and other assets.

Newton City Councilor Becky Grossman — who like Leckey is expected to pour some of her own money into her campaign to help finance the final stretch — committed to releasing one tax return, for the most recent years. Her husband, Ben Grossman, has been co-president of his family’s marketing company since his father, Steve Grossman, stepped down to run for state treasurer in 2010.

“Our campaign is committed to transparency and providing voters with all the information they need to make their decision,” Grossman campaign manager Alex Vuskovic said in an email. “We will be releasing Becky’s 2019 tax returns after it is completed in the coming days.”

Grossman’s personal financial disclosure lists 14 pages of investment and other assets, including a stake in the Grossman family business worth at least $1.5 million. Grossman also disclosed her participation in the pension plans of two of her former employers, Goldman Sachs and Goodwin Procter LLP.

Dave Cavell, a former state assistant attorney general, expects to release his 2019 and 2018 tax returns by Thursday, “and then we will continue releasing further back,” spokesperson Alexandra Caffrey said in an email.

Ben Sigel, an attorney, said he has not filed his 2019 tax return yet but will release it once it’s finished. “I believe in transparency for our Members of Congress and elected officials, so I will happily release my tax returns when the other candidates do the same,” he said in a statement, adding, “I will release the same number of years as the other candidates so we are all consistent.”

The Democratic nominee in the 4th District will take on the winner of the Republican primary between Julie Hall and David Rosa in the November election.

Ted Nesi (tnesi@wpri.com) is WPRI 12’s politics and business editor and a Target 12 investigative reporter. He is a weekly panelist on Newsmakers and hosts Executive Suite. Follow him on Twitter and Facebook