"If you are one of the Globe's disproportionately white, well-off, well-educated readers, the past few decades have been pretty good for you. The status quo has delivered. Ed Markey has done just fine," Clemons wrote. "But if you are one of the hundreds of thousands of normal, working people in this Commonwealth, if you are Black or Brown, if you are an immigrant or a veteran, if you are sick or struggling or suffering — you know that business as usual isn't working."

When Kennedy entered the race last year, polls showed him ahead of Markey by double digits, and he consistently bested the incumbent senator in campaign donations. But with primary day approaching, both campaigns acknowledge they are locked in a much tighter primary race than before. Kennedy and Markey raised about the same amount of money in the most recent fundraising quarter. There has not been reliable public polling of the contest in months.

The Globe cited Markey's advocacy on climate change as one reason for its endorsement, and suggested Kennedy "lacks the chops and track record" on climate change that Markey can provide as the co-author of the "Green New Deal." The newspaper's decision to back Markey was "something we fully anticipated," Clemons wrote in reaction to the endorsement.

"The Globe editorial board had their mind made up about Joe since before he even got in this race," he noted. "We heard the final decision was a close call, but in the end, the establishment voices won out. Add it to the long list of forces in this state that circle the wagons when the status quo gets challenged."

The editor of the Globe's editorial page, Bina Venkataraman, defended the endorsement process on Wednesday, calling it "intense and rigorous."

"We in no way had a prebaked decision. It was an intense and rigorous deliberation, involving endorsement interviews with both candidates, that seriously took into account communities of color including those disproportionately affected by impacts of climate change," Venkataraman wrote on Twitter. "The Globe editorial board, and I personally, have tremendous respect for Joe Kennedy and for his commitment to Massachusetts and its communities."

Clemons said the campaign "worked the board tirelessly" to secure its endorsement but came up short.

The endorsement appeared in print on the same day a Globe investigation, separate from the editorial board, reported Markey spent the least time in Massachusetts of any lawmaker in the state's congressional delegation over the past several years. Kennedy has made Markey's relative absence from the Bay State central to his pitch to voters.

In several recent Democratic primaries, the Globe has sided with challengers who went on to defeat incumbents. The paper endorsed Rep. Ayanna Pressley against longtime former Rep. Michael Capuano in 2018, and also endorsed Rep. Seth Moulton's successful bid to oust former Rep. John Tierney in 2014. The Markey endorsement appears to be the first time the Globe has endorsed an opponent to a Kennedy since the 1960s.

With two well-liked lawmakers on the ballot, the insider-outsider dynamic is muddled in the Kennedy-Markey race. Kennedy is the challenger yet has a fundraising advantage, an edge in polling, a massive online following and a famous last name. To compete, Markey's been forced to pull from the insurgent playbook.

In the email, the Kennedy campaign also took aim at a Globe columnist, Scot Lehigh, who authored a series of critical pieces about Kennedy, including one under the headline: "It’s TV’s best new comedy: Why is Joe Kennedy running for the US Senate?"

"Let's win big on September 1 and show Scot Lehigh just how out of touch he is…" Clemons wrote.

“Nick's a good guy. I have no problem with him rallying the troops by taking a poke at me. But I am just one voice among many on the board," Lehigh said in an email.