WASHINGTON -- To a casual observer, the halls of Congress look pretty white. But according to Anthony Thomas, people of color abound there, so long as you know where to find them.

"It's all black and Hispanic people downstairs," said Thomas, a 23-year-old African-American from the suburb of New Carrollton, Maryland.

Thomas works as a dishwasher in the Senate cafeteria in the basement of the Dirksen building. His duties include catering special parties held in the Capitol and the Senate office buildings, where lawmakers and staff rub elbows with lobbyists and other power brokers. Though there are exceptions, it's mostly white people drinking and dining, and people of color like Thomas cleaning up after them, he said.

A report released in December by the Joint Center for Political and Economic Studies found that the most influential Senate staffers are disproportionately white. Among senior-level Senate staff -- chiefs of staff, legislative directors and other folks who ultimately shape the laws we all live by -- a mere 7.1 percent are people of color, researchers found. Yet people of color comprise 36 percent of the U.S. public at large. (There may well be more diversity among mid- and low-level Senate staff, but no such numbers are available.)

So where is all the Senate's diversity? Apparently, much of it is concentrated at the opposite end of the power structure.

For the past year and a half, a group called Good Jobs Nation, funded by the Change to Win federation of labor unions, has been organizing janitorial and food workers in the Senate offices and the U.S. Capitol Visitor Center. The group compiled a database of 160 rank-and-file employees it assumes would be eligible to vote if workers filed for a union election. (SEIU, a member of Change to Win, lost a union election among Senate dining employees three years ago, though the union could file for another election.)

When the group examined demographics, it found the makeup of the service workforce to be the exact opposite of the senior-level Senate staff.

The low-wage workers were almost exclusively people of color -- a whopping 97 percent, according to a demographic breakdown Good Jobs Nation provided to The Huffington Post (the breakdown did not identify individual workers). That number shouldn't be all the surprising, given the demographics of D.C. -- a majority of residents are people of color -- and the way low-wage food and janitorial jobs already skew heavily toward minorities in the U.S. at large, according to the Bureau of Labor Statistics.

A caveat: This was not a scientific study. The database was compiled through on-the-ground outreach done by the group's organizers, not through government records or an official survey. And since the group is only organizing rank-and-file employees, the numbers don't account for middle management, where the workforce appears more mixed. Yet the figures should ring true for anyone who's taken a close look at the workers cleaning the dishes and mopping the floors in the Senate.

"I think what's happening at the Capitol reflects a larger trend in our economy -- the gap between the knowledge economy workers and the service-sector workers," said Joseph Geevarghese, director of Good Jobs Nation. "You've got a class of workers who are higher paid, and then you have an underclass of service workers who are low-paid and struggling to make ends meet."

Geevarghese's group has been agitating for raises for the workers at the Capitol, along with a host of other federal sites around Washington, including the Smithsonian and Union Station. It has succeeded in pressuring President Barack Obama to issue an executive order mandating a minimum wage of $10.10 per hour for workers on federal contracts. It also has gotten a lot of U.S. senators on board with the call for a $15 wage floor and a union in the Senate buildings, with Sen. Bernie Sanders (I-Vt) and Democrats sending a stern letter to one of the main Capitol contractors, food giant Compass Group.

There's a simple explanation for the campaign's growing political support: It's embarrassing that many of the people who take out lawmakers' trash and make their lunches are struggling to cover basic needs in one of the country's most expensive cities. It's also emblematic of larger trends in income inequality around the country. As The Washington Post reported last year, one employee, Charles Gladden, has periodically been homeless while working as a janitor in the Senate.

The racial disparity should be just as unsettling, said the Rev. J. Herbert Nelson, director of the Presbyterian Office of Public Witness, which leads the church's social justice efforts. Nelson has been a backer of the campaign, showing up for rallies and strikes to speak to workers.

"These people are really unseen in the public square, and there's no real intermingling across economic lines -- not just in the Senate buildings, but out in society," Nelson said. "We have some significant struggles with regards to race, wage earning and how individuals are selected to serve in positions of power. Work is racialized, and that's the great challenge that we have."

Arhmed Claggette, 30, works as a janitor cleaning bathrooms in the Senate buildings, earning $11.83 per hour, a wage that he said doesn't cut it in Washington. He said he took part in one-day walkouts because many of his colleagues have gotten only small raises after years on the job. He said the racial disparity between those who run the Senate and those who clean it is hard to miss.

"It would make a difference if the people who work with the senators could shed a little light on what it's like for people like me to struggle," Claggette said.

The Senate cafeteria workers recently won a raise through a new contract. The average pay for the 115 workers under the contract is supposed to rise from $13 to $14.50, though some workers have claimed they were quickly reclassified into different positions, negating the pay hikes. Under federal contracts, workers' wages fall within a certain range for their occupations, so a lesser title means less pay. One cook told The Washington Post he was downgraded to a "food service worker," which amounts to a difference of nearly $3 per hour.

Anthony Thomas, the dishwasher, said his base pay recently went up a dollar, to $13.30, and believes the recent protests played a big role in the raise. But even with the bump, he said he feels he should earn more, given the nights and odd hours he has to work for special events. His goal is to rise to the position of cook, to be in a better position to support his fiancee and their 6-month-old son. The splendor of the Capitol, he said, has a way of reminding him of his financial struggles.

"Sometimes I'll walk around and think, 'That column right there is worth more than my salary,'" he said.

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