U.S. Reps. Donna Edwards and Chris Van Hollen, both Democrats, are battling in a hotly contested primary race to succeed Maryland Sen. Barbara Mikulski. (Mark Gail/The Washington Post)

The chief executives of Maryland’s two largest jurisdictions joined other top politicians and labor leaders Friday to denounce one of two candidates running Maryland’s closely contested Democratic Senate primary race.

During a call with reporters Friday, two prominent African American Democrats — Montgomery County Executive Isiah Leggett and Prince George’s County Executive Rushern L. Baker III — emphasized their preference for Rep. Chris Van Hollen (D-Md.), who is white, over U.S. Rep. Donna Edwards (D-Md.), who if elected, would become the first black female senator from the state.

“Diversity is important,” Baker said. “But what’s more important is [electing] people that get things done.”

Van Hollen’s decision to gather the congresswoman’s detractors to criticize her record is a sign of how heated the race has become, with less than three weeks until the April 26 primary. A Washington Post-University of Maryland poll this week shows a statistically insignificant lead for Edwards in a race that splits voters along racial lines.

Edwards’s spokesman, Benjamin Gerdes, declined to comment on the criticism levied by his boss’s fellow Democrats, other than to say: “With the exception of his proposal to raise property taxes by 15 percent, Donna’s always enjoyed a productive relationship with County Executive Baker, and we’re sorry to see him stoop to personal attacks so close to an election.”

Baker called his administration’s relationship with Edwards “non-existent,” and said she had shown a lack of leadership in early conversations with federal officials about the FBI headquarters moving to Prince George’s.

He recalled that early in his administration, he arranged meetings on Capitol Hill to review county priorities. A meeting with Sen. Benjamin L. Cardin (D-Md.) ran late, into the time Baker had scheduled with Edwards and Van Hollen.

Both representatives had to leave their offices to vote on the House floor. But while Van Hollen later carved out a few minutes for the county executive, Edwards did not, Baker said.

“Chris has been there,” said Baker, who is joined in backing Van Hollen by other senior Democrats from the county, including state Sens. Joanne C. Benson, Ulysses Currie and Victor R. Ramirez.

“It’s become apparent that the people who know her best are not supporting her,” Baker said.

Leggett said he believes voters are still getting to know Van Hollen, whom he described as someone reluctant to boast about his accomplishments.

“Once they see and understand his record, those numbers will change,” Leggett said.

Former Maryland delegate Heather R. Mizeur (D) and representatives from two unions were also on the call. Ricarra Jones of the Service Employees International Union said Edwards betrayed labor organizers when she supported the “notoriously anti-union” Washington Adventist Hospital and its bid to relocate its facility a few miles from another hospital that is facing downsizing.

As a result, several of the union members lost jobs, Jones said.

Matt Biggs, of the International Federation of Professional and Technical Engineers, said that when African American NASA workers brought Edwards allegations of racial bias in performance reviews, the congresswoman did nothing.

Edwards defended her office’s response to the NASA workers at a recent forum, saying she has been working on the issue and the group was simply dissatisfied with the result.