In a rapidly diversifying county, Eastern Montgomery’s District 5 is ground zero.

Stretching from Takoma Park to north of Burtonsville, bounded by D.C., Prince George’s and Howard counties, it has the largest minority population in what is now a “majority minority” Montgomery. Sixty-two percent of district residents are African American, Hispanic or Asian. District 5 is also the setting for what is shaping up as 2014’s most hotly contested County Council primary.

It got hotter Tuesday with the announcement that a group of Democratic leaders headed by Valerie Ervin — who held the seat for seven years until her resignation in January — will formally endorse Board of Education member Christopher Barclay

Ervin, who is African American, said she considers District 5 a “legacy seat,” meaning that whoever holds it should reflect the area’s diverse electorate.

Barclay, 53, a two-term board member, is one of three African Americans in the five-way contest, along with Takoma Park community organizer Terrell North and nonprofit leader Jeffrey Thames. State Rep. Tom Hucker (D-Montgomery) and Silver Spring activist Evan Glass, the other two candidates, are white.

“People get nervous in Montgomery when you talk about race and politics. But it’s clear this is an issue,” said Ervin, who left the council to head up a nonprofit advocating for working families. Prior to Ervin, the seat was held by Tom Perez, the council’s first Hispanic member and now U.S. Secretary of Labor.

As Ervin suggests, not all of Barclay’s supporters are likely to be comfortable framing the contest around race. But on Wednesday morning at the Silver Spring Civic Center, a large contingent of local leaders is expected to close ranks behind Barclay. They include the Montgomery Council’s two other African-American members, Council President Craig Rice (D-Upcounty) and the District 5 caretaker who is not running in the June primary, Cherri Branson (D-Silver Spring). Also expected to attend are Council member Nancy Navarro (D-Midcounty), and two of Barclay’s Board of Education colleagues, Shirley Brandman and Michael Durso.

Barclay, who served as board president in 2010 and 2013, said Tuesday he was “very excited” about the endorsements. He said he agreed with Ervin about the need for the seat to reflect the district’s diversity but added: “I think that first and foremost I’m highly qualified for the seat. This campaign is about the issues, it’s about the people of District Five and who can best represent them.”

Other contenders downplayed the significance of the announcement. Glass, who if elected would be the first openly LGBT council member, said: “District 5 is a beautifully diverse district. I will work on behalf of all residents to move the county forward regardless of race, gender or sexual orientation.”

“Honestly, I’ll just have to work harder,” said North.

Thames called the endorsements “unfortunate,” and described himself as “the only one that will fight for working families.”

Hucker, reached late Tuesday afternoon, said it was the first he’d heard of the endorsements and wanted to think about it before responding.

This is the second big boost in recent weeks for Barclay, who last month was endorsed by the county teachers union, the Montgomery County Education Association (MCEA). That gives him a spot on the coveted Apple Ballot, which is mailed to registered Democrats and distributed near polling places on Primary Day.

The teachers’ choice reflects the other set of tensions playing out in District 5. While it is easy to look at labor in monolithic terms, the contest is a reminder that Montgomery’s public employee unions have distinctly different needs and objectives.

Hucker, a founder and former executive director of Progressive Maryland, has strong ties to the labor movement and especially the senior leadership of MCEA. He has won their endorsement for his state legislative campaigns. Under almost any other circumstance, he’d have received it again for his council run.

But as a Board of Education member Barclay has been an important player for the MCEA, working closely with the union on budgets and other policy questions. He also has two years left on his term and does not have to resign to run for council. For the teachers, that means endorsing Hucker would result in one of two outcomes, both bad. A Hucker victory would lead to an awkward-at-best two more years of doing school board business with Barclay. A Barclay win would install an alienated ally on the County Council.

Hucker, meanwhile, has been endorsed by unions long frustrated with the teachers’ dominance of county spending (school funding comprises more than half of Montgomery’s operating budget).

The United Food and Commercial Workers (UFCW) Local 1994, also known as Municipal and County Government Employees Organization (MCGEO) represents about 10,000 non-uniformed Montgomery workers. Along with the International Association of Fire Fighters Local 1664, they are especially unhappy that MCEA lobbied successfully in Annapolis a couple of years ago to tighten the so-called “maintenance of effort” law that mandates minimum levels of local education spending as a condition of state funding. They believe that the law has taken money and benefits off the table that could have gone to their members.

Adding to the backstory is Ervin’s turbulent relationship with MCGEO president Gino Renne. A one-time UFCW organizer, Ervin clashed with Renne on a series of measures, including changes in collective bargaining and disability retirement rules for police.

The tensions grew personal. Renne unsuccessfully sought a county inspector general’s investigation of alleged ethical violations on Ervin’s part. She charged that MCGEO was behind an anonymous Web site that smeared her. Renne denied any connection to the site.

Ervin says she’s not interested in payback, but it’s no accident that she and Renne once again find themselves on opposite sides.

In announcing its endorsement of Hucker a few weeks ago, MCGEO said District 5 was “its top priority this election season, and will launch a robust political program including weekend door knocking and phone banks.”