First, the protracted nomination fight between Hillary Clinton and Bernie Sanders divided the national Democratic Party. Then, in March, it split Massachusetts primary voters clean down the middle, Clinton eking out a victory of less than 2 percent.

Now, the ongoing contest is threatening to cleave the state’s most ardent Clinton loyalists themselves, as an internecine battle unfolds over who will fill the former secretary of state’s roster of delegates at the Democratic national convention in July.

While presidential primaries historically have been largely decided before the race swings through Massachusetts, this one was still fairly tight when it arrived. And, because the March 1 primary was so close, Clinton emerged with just one more delegate than Sanders. That has party activists — a heavily pro-Clinton bunch — squabbling over a limited number of delegate seats up for election Saturday, and those on the outside angry about being explicitly excluded by the Clinton campaign.

“I think it’s a travesty,’’ said David J. Holway, national president of the National Association of Government Employees. “When you have a candidate that’s supported by a large group of people and then to have them snubbed in the delegate selection process, it takes people’s enthusiasm away to be snubbed like this. I think it’s unprecedented.’’

Several Clinton supporters said they were pained by the furor but planned to stick with their candidate.

“People were unhappy with the campaign, and I was one of those. But I’m moving on,’’ said state Representative Kay Khan, a Newton Democrat who has long supported Clinton and was one of her delegates at the 2008 convention. Khan and others said the intraparty bitterness in 2008, when Clinton and then-Senator Barack Obama dueled far into the primary calendar, does not approach this campaign’s.

“Maybe there was animosity I wasn’t aware of, but I don’t think it was the same as it is this time,’’ Khan said.

The delegate selection process is complex but could devolve into an old-fashioned political scrum Saturday when the committee gathers in Newton to pick delegates. Both the Sanders and Clinton campaigns have prepared slates they would like to send to the convention in Philadelphia. And both campaigns have the right to refuse any candidates who try to win their own seats, though the Sanders campaign has not threatened to do so, according to multiple Democratic sources.

The limited number of seats has roiled longtime Clinton allies and was a hot topic at the state party’s annual Roosevelt Dinner on Monday, after an e-mail last Friday from a Clinton campaign official.

Charles Baker III, the campaign’s chief administrative officer and president and cofounder of the Dewey Square Group public affairs firm, told Clinton backers that “almost 97’’ of them had applied for 16 at-large and “party leaders and elected officials’’ delegate slots.

“I am writing to inform you that, unfortunately, your name will not be eligible to be entered into nomination for one of these positions,’’ Baker wrote. He did not respond to phone messages.

The missive angered some Clinton supporters.

“It is an interesting strategy when the campaign as a whole is attempting to be inclusive and bring new people in,’’ a former state party official said.

The official, speaking anonymously to discuss party matters, said the move had effectively snubbed nearly “a hundred activists who are supportive of Hillary, knocked on doors for Hillary, made phone calls for Hillary. They can’t even run or attempt to run. . . . They’re being told they can’t because the Clinton campaign has specifically picked people.’’

In a statement e-mailed by a campaign spokeswoman, Baker said, “Unfortunately, we can only select a limited number of those individuals to represent the campaign in Philadelphia. We look forward to selecting the best possible delegates on Saturday.’’

Holway, the union leader, wrote to state committee members arguing that the Clinton camp’s move to deem some delegate hopefuls ineligible had “corrupted’’ party rules.

One veteran state committee member, Robert Colt of Winchester, sounded out colleagues — including Khan — about running an alternative slate, but he has backed off the plan.

“It was just going to make it a really horrible situation on Saturday,’’ Khan said.

Indeed, loyalty to Clinton appears to have prevented the ill feelings from boiling over.

“I’ve probably worked longer and harder than anybody else who’s running over 25 years for the Clintons, particularly for Hillary, but that’s really not the issue,’’ former state senator Lois Pines said. Pines said she had planned to run and had begun courting other members but opted against it.

“All these people should’ve gone out and fought harder to get more Hillary Clinton delegates,’’ Pines said, referring to the primary results. “It doesn’t help to complain. It’s too late.’’

Complicating the delegate selection process are new rules designed to boost diversity in the delegation.

Jesse Mermell, who was communications director in the Patrick administration and is now president of the Alliance for Business Leadership, said she had wanted to be a delegate and still hopes to find her way to Philadelphia in some capacity but understands why she was not included on the Clinton slate.

“I am a white woman from Brookline in a year when the party is making a real commitment to putting together a diverse slate of delegates, and the campaign had the same commitment. The fact that I don’t add a lot of value to that dynamic is not something I take personally,’’ she said.

The unrest comes as Clinton, a likely nominee with historically high unfavorability ratings, works to persuade Sanders backers to unite behind her. She now figures to face the presumptive Republican nominee, Donald J. Trump, whose negative public image outpaces even hers.

And the furor further underscores a delicate moment in state Democratic politics. Since former governor Deval Patrick left office, the party has struggled to coalesce behind a top Democrat, leaving a vacuum across the aisle from Republican Governor Charlie Baker.

In all, Massachusetts will send 116 delegates to Philadelphia. Fifty-nine of those were elected at congressional-district caucuses last month, a process that brought its own round of internal political intrigue as party powerbrokers ran their own slates of supporters.

Braintree Mayor Joseph Sullivan won an 8th congressional district slot and said he hopes to bring “pragmatism and moderation’’ to the convention.

Sullivan, a former legislator who appeared publicly with Baker the day before the 2014 gubernatorial election, added, “I’m going as a Democrat, hopefully representing a section of the party that still exists.’’

Jim O’Sullivan can be reached at jim.osullivan@globe.com. Follow him on Twitter at @JOSreports.