Rep. Chris Van Hollen (D) visits the United Way Family Center in Baltimore’s Benjamin Franklin High School. (Amanda Voisard for The Washington Post)

On a recent Saturday in Baltimore, Rep. Chris Van Hollen spent the morning at a ceremony for black veterans, the afternoon at a celebration of Black History Month and the evening at a basketball game between two historically black universities.

Across town, his rival, Rep. Donna F. Edwards, convened a meeting of about 50 female supporters, including her mother and sisters.

Charm City has become the key battleground in Maryland’s competitive Democratic Senate primary, thanks to a cheap media market and a lack of homegrown candidates. With polls showing Van Hollen winning his base of Montgomery County and Edwards her home of Prince George’s County, both candidates are focusing their firepower on Baltimore, whose voters are up for grabs.

The April 26 primary comes at the end of a particularly rough year for Baltimore, including a growing homicide rate and rioting last April over the death of Freddie Gray after he had been in police custody. Since then, the city has engaged in a different kind of battle, fighting a Republican governor who canceled a long-planned light-rail project and has clashed with city leaders.

Rep. Donna F. Edwards (D) campaigns in Baltimore. (Rachel Weiner/The Washington Post)

Whoever wins the primary will be the overwhelming favorite to triumph in November’s general election and succeed retiring Sen. Barbara A. Mikulski (D-Md.), the longest-serving woman in Congress and a lifelong Baltimore resident. The city and Baltimore County have nearly 600,000 registered Democrats, according to 2014 figures from the state Board of Elections, compared with a little under 800,000 in Montgomery and Prince George’s.

Each candidate has made more than 100 appearances in Baltimore since the campaigns began, aides said. Van Hollen has the endorsements of powerful Baltimore politicians and the money to blanket the city with ads. But Edwards, an African American single mother from Prince George’s who has struggled to raise funds, has support from a deep-pocketed super PAC. She also has a natural demographic advantage in a city electorate that in the 2008 primary was 58 percent female and 62 percent African American.

Recent polls show the candidates about even, although the latest Baltimore Sun poll had Edwards in the lead. On Sunday, they both visited Coppin State University for a candidates’ forum sponsored by BUILD (Baltimoreans United in Leadership Development).

Edwards needs to boost turnout in Baltimore as much as possible. It is a goal made easier because of the city’s high-profile and competitive mayoral primary, whose two front-runners — former mayor Sheila Dixon and state Sen. Catherine Pugh — are also black women. She also needs to win over at least some of the white voters in the suburbs.

Van Hollen’s challenge is to generate enthusiasm among suburban voters, while not sacrificing the city vote entirely.

“If I was Van Hollen, I would be worried about turnout in the county,” said University of Baltimore professor John T. Willis, noting the lack of significant local races on the suburban ballot. “On the other hand, there is a very heavily contested open race for mayor in the city, and you have half a dozen candidates that have several hundreds of thousands of dollars that they are going to use to turn out voters.”

Edwards “looks like our core voting demographic,” said Mileah Kromer, a political science professor and pollster at Goucher College. “She has a built-in affinity with these voters, and he doesn’t.”

Still, there was Van Hollen at Baltimore’s Reginald F. Lewis Museum last month, telling the mostly black crowd that he had taken his daughters to walk over the famous bridge in Selma, Ala., where the Rev. Martin Luther King Jr. once marched. It was an anecdote that resonated with Dianne Graham, a 60-year-old from the city’s Canton neighborhood who said she makes her living as a crossing guard and a wedding singer.

“I like his style,” Graham said. “I think he’s for the folks.”

Others at the museum expressed enthusiasm for Edwards. “She’s very approachable; she’s down to earth; she’s a woman,” said Cheryl Boston, a 63-year-old retiree.

“I like her overall aura, her way of speaking,” said Evangeline Armstrong-Fuller, 78, also retired.

A super PAC run by Emily’s List, the Democratic women’s group, is supporting Edwards and so far has exceeded Van Hollen’s spending on television ads. But Edwards has to fund her own field operations and has far less money to spend than Van Hollen. She also lags behind in support from and connections with prominent local politicians.

“We’re very grass-roots,” said Lauren Foster, 52, an engineer at Baltimore’s MET Laboratories, who volunteers for Edwards. “It’s going to make it a challenge.”

Van Hollen’s long list of supporters all over the city and county dates to his years as a state lawmaker in Annapolis. “Those relationships never die,” said Shawn Z. Tarrant, a former state delegate now running for Baltimore City Council. “It is a club, and you’re in the club.”

And Van Hollen has won new friends with tenacity. His campaign says he has reached out to “virtually every” Democratic council member and state lawmaker in Baltimore, along with church, labor and civic groups.

The congressman worshiped in the pew of city Comptroller Joan M. Pratt at West Baltimore’s Bethel A.M.E. Church on March 6 and made sure to touch base with Pugh at the event at the black history museum. Watching Morgan State eke out an overtime win at Coppin State in West Baltimore later that Saturday, he chatted up gubernatorial adviser Keiffer Mitchell, state Del. Antonio Hayes and State Central Committeeman Kevin Parson.

“He’s been very visible,” said Parson. “People can touch him.”

Tessa Hill-Aston, head of the Baltimore branch of the NAACP, said she was persuaded to back the congressman after getting a direct call from his wife. “I was impressed and intrigued,” Hill-Aston said. “You’ve got to ask people — Donna never reached out personally.”

Edwards, meanwhile, met last week in Baltimore with African American activists from across the state. On a recent Tuesday evening, she relied on her personality and her own compelling biography to connect with a gathering of leaders from northwest Baltimore neighborhood associations, hugging two people as she walked into the room.

She told the group how she rose from being an advocate for victims of domestic violence to a congresswoman fighting to expand after-school meals to students in Maryland. Her proclamation that children deserve great schools in Baltimore just as much as they do in Chevy Chase prompted loud rounds of “mmhmms,” as did her reminder that, if elected, she would bring diversity to the august legislative chamber.

“Nobody in the Senate is the mom of a young black man — a fine young man I must say — who understands what it’s like to raise a young black man in a really complicated environment,” Edwards said. “I believe today that is a perspective that is sorely needed in the United States Senate.”

Christopher Crockett, 55, said Edwards “spoke on things I know are real.”

“Raising boys? My mother raised four boys and a girl,” Crockett said. “She relates to struggles we had — and for poor whites, too, not just blacks.”

Van Hollen is looking for every possible advantage, including the argument that he — the son of a Foreign Service officer who was born overseas and lives in the Washington suburb of Kensington — should be considered the Baltimore candidate in the race.

“My family on my father’s side goes back generations in Baltimore,” he said in a recent radio interview. “My dad is from Baltimore; my cousins are all in Baltimore.”

That won him the support of Rikki Spector, a City Council member who last month took Van Hollen to a kosher bakery on the city border. She said she is encouraging religious Jews, many of whom could be out of town on primary day because it falls during Passover, to cast absentee ballots for Van Hollen.

“I’m really anxious that a Baltimore-based, a Baltimore-centered person represent us,” she said.

Fenit Nirappil contributed to this report.