A sliver of moon rises behind the Capitol dome. (Bill O’Leary/The Washington Post)

Errol Baker left his job at the Washington Hilton in 2004 after 12 years to pursue what he thought would be a better life working at the U.S. Capitol.

“I thought I was going to be working in a better environment,” he said. “I’d get to meet senators and congressmen and movie stars. I was very excited.”

Baker, 52, has brushed shoulders with the famous and the powerful in his years as a Senate food service worker — once, for instance, he received a $20 tip from then-Sen. Barack Obama — but he is otherwise no better off.

Unable to make ends meet on his $11.30 hourly wage, he now cleans offices for five hours at night after his eight-hour Capitol shift ends. It’s nearly midnight before he comes home to his D.C. apartment, hoping to catch a few hours of sleep before he reports to the Senate for his morning shift.

Baker is among a group of federal contract workers who are joining with union-backed advocates to call on lawmakers to do more to protect an increasingly privatized federal workforce, where low wages and minimal benefits often clash with the rhetoric espoused by elected leaders.

“We work for them every day,” Baker said. “They have a clean environment; they’ve got good food to eat. They say, ‘Thank you very much’ and ‘Good work.’ But that’s not enough. I need more so I can pay my bills. . . . $15 and a union.”

[ It’s not just fast food: The Fight for $15 is for everyone now ]

The national campaign for higher wages and better benefits — reflected in the “Fight for $15” backed by the Service Employees International Union — has landed squarely on Capitol Hill as the 2016 presidential race spins up.

“If the candidates can’t help the workers who cook and clean for them, how will they help the low-wage workers who labor all across America?” said Joseph Geevarghese, deputy director of the Change to Win labor coalition, a sponsor of the Good Jobs Nation campaign that is seeking to highlight job conditions among federal contract workers. “What happens at the Capitol is a litmus test about whether or not presidential candidates who know these workers really care.”

[ The homeless man who works in the Senate ]

A protest in April helped highlight the plight of Senate workers such as Charles Gladden, 63, who had been sleeping outside the McPherson Square Metro Station. On Tuesday, another Senate food worker, Sontia Bailey, wrote in the Guardian about having a miscarriage after working two jobs: Her full-time $10.59-an-hour Senate position, and an $11-an-hour part-time job at a Kentucky Fried Chicken restaurant.

On Wednesday, liberal members of Congress — including Sen. Bernie Sanders (I-Vt.), a Democratic presidential candidate — will appear on the Capitol grounds with worker advocates to call for a $15 minimum wage.

That proposal, which would more than double the current federal minimum wage, is almost certain to be dead on arrival in a Congress controlled by Republicans who argue that a minimum-wage increase would reduce the overall number of jobs. But advocates want President Obama to take executive action to improve standards for federal contractors, and there is hope that senators might try to improve the lives of contract workers such as Baker, Bailey and Gladden.

Senate food services were contracted out amid ongoing operating deficits in 2008, when Democrats were in the majority. “There are parts of government that can be run like a business and should be run like businesses,” Sen. Dianne Feinstein (D-Calif.), then-chairman of the Senate Rules and Administration Committee, said at the time.

The contract with New York-based Restaurant Associates is now up for review, and workers and advocates are pushing for a seat at the table to negotiate improvements for employees.

House workers have been unionized for nearly three decades, but Senate workers are not. Although the Restaurant Associates contract guarantees the right of workers to form a union, a 2012 SEIU-backed organizing drive failed.

[ Why House cafeteria workers are paid better than Senate cafeteria workers ]

A spokesman for Sen. Roy Blunt (R-Mo.), the current chairman of the rules panel, declined to comment on the ongoing negotiations, saying they are now between Restaurant Associates and the Architect of the Capitol, not the committee. Sen. Charles E. Schumer (N.Y.), the top Democrat on the panel, said the contract workers are “part of the Senate family and they deserve to be treated as such.”

“A $15 minimum wage and better benefits would be a great way to say thanks for all that they do, and we’re working hard to make it happen,” Schumer said.

A Democratic aide who is familiar with the process but was not authorized to comment on it publicly said that “some progress” has been made but that “there is more to be done.”

A report issued this week by the D.C. Fiscal Policy Institute and Good Jobs Nation found that tens of thousands of federal contract jobs, about 30 percent of the total, pay less than the D.C. living wage for a family of four. That includes the vast majority of grounds maintenance and food service jobs. That, in effect, the report says, makes the federal government one of the Washington region’s largest low-wage employers.

The wages and benefits offered to Senate workers are made even starker by the internal disparities between Restaurant Associates employees. Those who were hired before privatization — such as 33-year worker Norma Rogers, 76 — receive higher wages and robust federal benefits.

The newer workers “are treated like when they had slaves, you know? ‘You got to do what I tell you or otherwise you go,’ ” said Rogers, who earns $17 an hour. “With us, it’s a little different.”

When Baker was hired at the Capitol in 2004, he took a temporary job expecting to transition into a good-paying job with federal benefits like Rogers’s. That hope ended once food services were contracted out in 2008.

Had he stayed at the Hilton, Baker probably would be much better off: Under the latest contract negotiated by the union representing most D.C. hotel workers, Baker would make at least $18 an hour now, plus employer-paid medical and dental benefits.

Baker said he regrets coming to work at the Capitol. “I’m not going to lie to you,” he said. “Especially now.”