District voters on Tuesday embraced a ballot initiative that threatens to roil the city’s flourishing restaurant industry, voting to raise the minimum wage to $15 for servers and other workers who largely rely on tips to earn a living.

But the District’s political leadership has expressed opposition to Initiative 77, as the measure is known, and restaurant owners and workers are expected to pressure the D.C. Council to halt its enactment even though it passed 55 to 44 percent.

The vote in the nation’s capital is part of a national campaign; the same advocates are trying this year to raise wages for workers who earn gratuities in New York and Michigan.

The fate of Initiative 77 was the showcase drama on a day when Mayor Muriel E. Bowser, facing nominal opposition, won nearly 80 percent of the vote and cruised to victory in the Democratic primary. Her triumph positions her to become the first D.C. mayor in a dozen years to capture a second term.

A half-dozen council incumbents also won, including Chairman Phil Mendelson (D) and council member Anita Bonds (D-At Large).

About 18 percent of the city’s 479,723 registered voters cast ballots, the lowest turnout in a mayoral primary since at least 2010. Turnout ranged from 22 percent in Ward 3, the most affluent part of the city, to 7.7 percent in Ward 8, the most impoverished.

A New York-based advocacy group was behind the ballot measure to raise the wages of servers, bartenders, bellhops and others, arguing that they should not have to rely on tips to survive.

But the proposal — mandating that by 2025 businesses raise from $3.33 to $15 the required hourly wage — prompted fierce opposition from restaurateurs and workers who say it will drive up labor costs and force eateries to close.

Mendelson, who opposed the initiative along with eight other council members, declined to say whether he would seek to block it from becoming law. “I’m going to let the dust settle,” he said, while his supporters celebrated his victory at Brixton, a bar on U Street NW.

The initiative’s opponents vowed to press their case with District leaders.

“The issue of how people are to be fairly paid in the hospitality industry is a complicated one, not easily explained by campaign signs, slogans and buttons,” Kathy Hollinger, executive director of the Restaurant Association of Metropolitan Washington, said in a statement. “What is telling, however, is that tipped workers, the very workers who would supposedly be helped by the passage of Initiative 77, overwhelmingly opposed the measure.”

Jeff Black, who owns BlackSalt and Pearl Dive Oyster Bar, described the initiative as “singularly the dumbest, most ill-thought-out concept that has ever happened to the hospitality industry. Period. End of discussion.”

“You can’t afford to give somebody a 500 percent pay raise and not have it come from somewhere,” he said by phone from Texas. “All my best servers will leave this city. They will move out and … take jobs in Maryland and Virginia.”

The initiative’s proponents planned to rally outside the John A. Wilson Building on Wednesday morning to urge lawmakers to abide by the election results.

Andy Shallal, owner of Busboys and Poets, described the vote as a “huge game changer” for the restaurant industry. But he also acknowledged that small restaurants could be hurt. “This is not going to be an easy thing — pain is going to happen,” he said. “It’s part of growth.”

Trip Brennan, 25, a bartender on H Street NE, said he was surprised the measure passed despite opposition.

“I’m really excited. I’m really happy it passed,” he said during a quick break from a shift. He called on the council to respect the will of voters.

“For them to overturn it, I think would be a huge mistake,” he said. “It would hurt workers not help them. I think that they just need to see the people of the city decided this is what they wanted. They should work to make sure it’s implemented smoothly and ultimately benefits workers.”

At her victory party, held at Towndance Boutique, a gay dance club on U Street slated to be demolished and replaced by condominiums, Bowser drank a cocktail, mingled with supporters and danced to Luther Vandross’s “Ain’t No Stopping Us Now.”

Speaking briefly to a reporter, Bowser said she would meet with restaurant workers before deciding how to approach Initiative 77.

“I want to really sit down and evaluate its impact with restaurant workers and people affected and see if they will be able to afford a quality of life in the city,” she said.

Across the city, voters expressed frustration that they did not have more choices from the mayor’s race to the down-ballot contests.

With an overwhelming majority of registered Democrats in the District, the primary amounts to a general election, and Bowser’s victory almost guarantees her another term — unless an independent challenger emerges before the November contest.

Buoyed by the city’s prosperous economy, and a $2 million campaign war chest, the mayor has managed to avoid any serious competition despite a flurry of public school scandals and a surge in homicides that has unsettled residents, particularly in the District’s poorest neighborhoods.

After voting at Shepherd Elementary around 8 a.m., Bowser stopped at polling places around the city before eating lunch at Ben’s Chili Bowl. Her guests included two former mayors — Sharon Pratt Kelly and Adrian Fenty, her political mentor, whose photo she displays on her desk.

In interviews as they left polling places from Chevy Chase to Hillcrest, voters expressed a mix of sentiments about the mayor, from satisfaction with her overall tenure to frustration that she has not done more to keep the city from becoming too expensive for poor, working-class and middle-class residents.

“I haven’t been displeased with her performance so far,” said Carlos Martin, 48, a researcher who voted at an Adams Morgan church. “She’s a known commodity. .”

Across town in Ward 7, Alphonso Coles, 61, lamented the lack of quality choices in the race and said he chose Bowser because he hadn’t heard anything about the other candidates, disbarred lawyer James Butler and real estate agent Ernest Johnson.

“There weren’t as many names I recognized as being active in the community as I thought I’d see,” Coles said.

Paulette Tilghman, 70, a retired educator who voted for Johnson, complained that Bow­ser’s affordable housing initiatives are too expensive for the city’s neediest residents. “Affordable to whom? Not to the people I know,” Tilghman said.

Opposing Mendelson, a five-term council member seeking a second full term as chair, was progressive activist Ed Lazere. He hammered Mendelson as weak on issues of concern to the city’s most vulnerable residents.

But April Massey, 60, a Shepherd Park resident who is dean of the College of Arts and Sciences at University of the District of Columbia, said she was sticking with Mendelson.

“He has a complex set of issues and he has shown himself to be courageous,” she said. “The council looks more cohesive than it has in a while. He’s a steady force in a time of challenge, but also opportunity.”

Council member Brianne K. Nadeau (D-Ward 1) fought off three challengers — Kent Boese, Lori Parker and Sheika Reid — who sought to capi­tal­ize on what they say is dissatisfaction with her attention to constituent issues.

Bonds (D-At Large) defeated opponents Jeremiah Lowery and Marcus Goodwin.

Initiative 77 was the most contentious and confusing issue on the ballot.

In interviews, voters across the city said they struggled with how to vote on the initiative.

Michael Carey, 30, who works at the Patent and Trade Office, said he voted against 77 after talking to the bartenders at the Capitol Lounge Bar.

“This bar is very regular — it’s not trendy or new,” Carey said. “Even though the bar wasn’t very crowded at night, bartenders I talked to still said they will make more in tips. Tips might go away and the employer might have more control over the tips.”

But Cosby Hunt, an educator who lives in North Michigan Park, voted “yes” out of a concern for servers who don’t earn much in tips.

Samuel Northrop, Victoria Knight, Dariya Tsyrenzhapova, Peter Jamison, Reis Thebault, Teo Armus, Tim Carman and Rachel Chason contributed to this report.