Neither Reps. Edward MarkeyEd MarkeyA guide to the committees: Senate GOP sets sights on internet privacy rules Overnight Tech: GOP chairman to propose high-skilled visa overhaul | Zuckerberg's 5,700 word letter | Tech lobbies gear up ahead of internet fight MORE (D-Mass.) nor Stephen Lynch (D-Mass.) reached the required number of votes to receive an endorsement from one of Massachusetts's most prominent unions, the AFL-CIO.

It's a blow to Lynch's campaign, which is relying on union support to boost the candidate in the Democratic primary for the special election to replace Secretary of State John KerryJohn KerryFormer Obama officials say Netanyahu turned down secret peace deal: AP How dealmaker Trump can resolve the Israeli-Palestinian conflict John Kerry to teach at Yale on global issues MORE (D).

To receive the group's endorsement, a candidate needed two-thirds support of the Executive Council. The Council could, with a simple majority vote, decide against endorsing altogether; failing to receive that, the Council moved on to vote on each of the potential candidates individually. Neither received the necessary numbers.

The loss of the group's vote means it will not activate its members to canvass, volunteer or vote for either candidate in the primary election, though individual unions included in the umbrella group are free to endorse on their own.

Markey's campaign declined to comment, but a spokesman for Lynch's campaign, Conor Yunits, tweeted that Markey received two votes to Lynch's 32, an assertion that could not be independently verified.

He noted that Lynch has received, by their count, the endorsement of 44 local unions, while Markey has received the endorsements of two, and he suggested that the outcome of the vote may have been the result of from "pressure" from Washington.

"Too bad DC continues to apply pressure on behalf of chosen nominee, and not let Massachusetts Democratic process prevail," he tweeted.

Markey has received the endorsement of the Democratic Senatorial Campaign Committee, along with a number of prominent Massachusetts Democrats, and remains the frontrunner in the race. Lynch has, however, managed to narrow Markey's lead in the polls over the past month.

Massachusetts AFL-CIO President Steven Tolman pushed back on the assertion that the vote was anything but democratic.

"I haven't talked to [AFL-CIO President] Rich Trumka in four months. This was a democratic vote of a 72-member board," he said.

Tolman said that while "there was definitely some debate, and there were definitely some passionate feelings expressed over the past several weeks," the final decision, not to endorse, was "the best opportunity for us to unite" for the general election.

And he added that the group's decision not to endorse Lynch, who was a union member and advocate himself early in his career, reflected "that he was up against a 36-year member of Congress that had a 96-percent record in Congress."

--This article was updated at 10:56 a.m. on Saturday to correct the name of the Massachusetts AFL-CIO president.