Angela Alsobrooks, state’s attorney in Prince George’s county, announced her candidacy for county executive in a speech in Camp Springs, Md., on July 31. (Arelis Hernandez/TWP)

A labor union that helped propel Donna F. Edwards to Congress years ago is throwing its support behind one of her Democratic primary rivals, State's Attorney Angela Alsobrooks, in the race for Prince George's county executive.

Service Employees International Union 1199, which represents 10,000 health-care workers, is endorsing Alsobrooks because of her executive experience running the busy prosecutor's office in Prince George's. SEIU Local 400, another powerful and well-resourced union, will back Alsobrooks as well.

"There is a huge difference between an executive and a legislator," said Pat Lippold, vice president of political action for 1199. "It's a dramatically different skill set."

Other candidates in the June 26 primary are political newcomer Lewis S. Johnson, former Obama appointee Paul Monteiro and state Sen. C. Anthony Muse (D-Prince George's). They are vying to succeed County Executive Rushern L. Baker III (D), who is term-limited and running for governor.

Edwards has received considerable labor and progressive support. She was recently endorsed by four unions that had helped persuade her to enter the race for county executive. This week she won the backing of CASA in Action, the political arm of the immigrant advocacy organization; Progressive Maryland; and a different, also influential SEIU chapter, 32BJ.

But she could not get the support of SEIU 1199, which went all out for Edwards nearly a decade ago, when she successfully challenged a longtime incumbent Democrat to win a seat in Congress.

Former U.S. representative Donna F. Edwards holds a town hall meeting with a group of labor activists at the headquarters of UFCW Local 400 in Hyattsville, Md., on July 19. Union members were trying to draft Edwards to run for Prince George's county executive. (Astrid Riecken/For The Washington Post)

While in Congress, Edwards angered many SEIU leaders and hospital workers by backing the relocation of the nonunion Washington Adventist Hospital at White Oak, which put the facility in direct competition with the unionized Laurel Hospital. The SEIU members who worked at Laurel blame Adventist's move for a 2015 downsizing that converted Laurel into an ambulatory care facility.

The rift led SEIU to switch alliances in 2016, when Edwards sought the Senate seat being vacated by retiring Sen. Barbara A. Mikulski (D). The union placed its money, members and political prowess behind Edwards's primary opponent, Chris Van Hollen, who ultimately won the race.

Lippold said in addition to what the union saw as a betrayal involving the hospital, the organization believes that Edwards has a "lackluster reputation" in providing constituent services, which is a significant part of a county executive's job.

"It's hard to imagine she is going to have the chops to run that level of government," Lippold said. "She is a great woman, smart and progressive, but I'm not so sure this is the best fit for her."

Many union members also support Alsobrooks because of their own experiences working with her in the court system or the many school and community programs she operates through her office, Lippold said.

"This is not about Donna F. Edwards. Their support for me is about going with someone who can get stuff done," Alsobrooks said. "They told me they are interested in supporting candidates that can deliver. Their endorsement is a vote of confidence in my leadership."