Rep.-elect Alexandria Ocasio-Cortez (D-N.Y.) said she will pay interns more than the minimum wage. (Melina Mara/The Washington Post)

When Rep.-elect Alexandria Ocasio-Cortez (D-N.Y.) said last week that she would not only pay her interns, but also provide more than the minimum wage, the news had an immediate impact.

National media covered the announcement. Liberal lawmakers promised to follow suit. Even ­A-list celebrities took note.

“Thank you for doing this,” R&B hitmaker John Legend tweeted to his 12.3 million followers. “Unpaid internships make it so only kids with means and privilege get the valuable experience.”

Within hours, the mood had perceptibly shifted on a parochial concern that has vexed Congress for more than two decades, as the progressive ideals of one incoming lawmaker ran headlong into the disparities that have long persisted on Capitol Hill.

Ocasio-Cortez is not alone. With its historic diversity and public following, the incoming class of House Democrats is already exerting power on an institution that for years has defied reform on matters concerning the thousands of staff and interns who carry out its work.

Congress performs terribly on metrics related to staff diversity, workplace protections and employee pay and benefits. Advocates warn that the system is built to accept only the most privileged young people — often white, moneyed and with connections — who later fill the pipeline for Washington’s political and business establishment.

The system has gone unchallenged for years. But scrutiny by Ocasio-Cortez and her peers after the recent midterm elections is stirring hopes that Capitol Hill might be ready for change.

“Five years ago, I could have lit myself on fire talking about staff pay, and nobody would have paid attention,” said Daniel Schuman, policy director of Demand Progress and an advocate for institutional reform in Congress.

“Ocasio-Cortez isn’t a conventional politician, so she’s talking about things that nobody would ever talk about otherwise. And it feels like a breath of fresh air because it is one,” Schuman said.

The pressure to pay interns comes at an opportune moment, as congressional offices gain access to a small amount of funding to do it for the first time since the mid-1990s. The money is already available to Senate offices and will become available to House offices next year.

The pool of money was the result of lobbying by Pay Our Interns, a small D.C. nonprofit run by two 24-year-olds whose goal is to increase socioeconomic diversity among congressional staff.

Carlos Mark Vera, the group’s founder and executive director, said he persuaded several Democratic lawmakers to pay interns by noting the possible political fallout if they didn’t.

“In meetings this year, we would say: ‘Look, midterms are coming up. You’re going to have to talk about the minimum wage. Many voters see you as out of touch, right? So it looks very hypocritical if you’re telling people, ‘You need to pay your workers $15 an hour’ and you’re not paying your interns a peanut,’ ” Vera said.

Workplace issues on Capitol Hill such as staff pay, diversity and protection from sexual harassment have the potential to become relevant as Democrats begin competing for the party’s 2020 presidential nomination.

The party lagged behind the GOP on paying interns as of last year. Among the dozen-plus congressional Democrats who have been discussed as possible White House contenders, only eight currently offer stipends or an hourly wage to at least some interns.

At 29, Ocasio-Cortez is in a unique position to call attention to these issues. The former waitress has noted on Twitter and Instagram that she will receive more- generous benefits as a member of Congress than she did in the food service industry, including less expensive health insurance. She has also spoken about the challenge of paying for a D.C. apartment before she starts earning her new salary.

Vera said most incoming lawmakers would be attacked or dismissed if they talked like this.

“That’s not sticking on AOC — you can’t make that argument with her,” he said.

The debate highlights the fact that despite the power and prestige of jobs on Capitol Hill, Congress has faced accusations that it treats many of its workers poorly.

Most aides earn at least 20 percent less than their peers in the private sector, experts say. Staffing has been cut even as the U.S. population grows. Employee benefits vary widely. And the high level of stress is exacerbated by long hours and cramped workspaces.

As Ocasio-Cortez notes, lawmakers who are not wealthy struggle, too. Shuttling back and forth to Washington creates the need for two homes. Some members, including outgoing House Speaker Paul D. Ryan (R-Wis.), have chosen to sleep in their offices to save money.

“It is a struggle, I’m not going to lie,” said Rep. Terri A. Sewell (D-Ala.), who was a partner at a law firm before she came to Congress. “It’s worth it every day to be able to help my home district and to give the opportunities that I was so fortunate to have to the children of my district . . . but it is a sacrifice.”

A former Capitol Hill intern, Sewell is one of the handful of House Democrats who already offers paid internships, understanding how difficult it can be to work for free.

“I literally slept on a pull-out couch in Silver Spring, Md., from a distant cousin to make that happen,” she said of her House internship in the 1980s.

Congress is considerably less diverse than the general public. Paying interns, increasing staff salaries and creating lawmaker housing have been proposed as ways to lower the barriers to entry and allow a more diverse array of people to work on Capitol Hill.

Yet political concerns have generally cut against taking these steps.

Bradford Fitch, president and CEO of the Congressional Management Foundation, said it’s almost impossible to get lawmakers to do anything that could be interpreted as “spending money on themselves.”

“That’s why they cut their own budgets,” Fitch said. “I remember talking to a senior staffer and asking, ‘Why are you doing this?’ And he said, ‘It’s for symbolic reasons.’ ”

One Democratic aide expressed concern that political pressure to offer paid internships could lead offices to eliminate unpaid internships, reducing opportunities for young people of all backgrounds.

“All of this attention is going to unintentionally hurt anyone who wants to be an intern,” said the aide, who started their career as an intern while also waiting tables and requested anonymity to discuss a sensitive issue on Capitol Hill. “This is going to backfire and make it worse and more undemocratic than before.”

Arguing that the number of internships on Capitol Hill is inflated, Vera said offices should consolidate positions to ensure each one involves substantive work and focus on offering paid spots to lower-income applicants.

“It wouldn’t hurt for some programs to reduce their intern classes,” he said. “You have them stapling and meanwhile, they’re taking out a loan to be there. I don’t know if that’s very helpful.”

The rising pressure on members was clear this week when Senate Minority Leader Charles E. Schumer (D-N.Y.) called for internship applications for the winter season and listed the position as unpaid. Under fire, the office said the language had been a mistake. Schumer plans to begin offering a stipend to “eligible interns” in January, the office said.

Of the current highest-ranking congressional leaders, only Schumer and Ryan do not already pay at least some interns, according to a survey by The Post.

Pay Our Interns listed each member of Congress and whether they paid interns in a report last year. Among Democratic lawmakers, only 3.6 percent in the House and 31 percent in the Senate offered paid internships. Among Republicans, 51 percent in the Senate and 8 percent in the House offered paid internships.

Shame soon became an effective tactic on the left, as prominent liberals began to change their policies.

Possible 2020 presidential contenders who pay at least some interns include Sens. Cory Booker (D-N.J.), Sherrod Brown (D-Ohio), Kamala D. Harris (D-Calif.), Jeff Merkley (D-Ore.), Bernie Sanders (I-Vt.) and Elizabeth Warren ­(D-Mass.), and Reps. Tim Ryan ­(D-Ohio) and Seth Moulton ­(D-Mass.).

Other possible candidates in the Senate, such as Kirsten Gillibrand (D-N.Y.) and Amy Klobuchar (D-Minn.), do not pay interns. Gillibrand plans to begin offering a need-based stipend in January using the newly available funds, her office said. Klobuchar will start paying all interns on Jan. 1, her office said.

In the House, Rep. John Delaney (D-Md.) — who has already declared his candidacy for president — does not pay interns, according to the 2017 report from Pay Our Interns. His office did not respond to questions from The Post.

Reps. Eric Swalwell (D-Calif.) and Tulsi Gabbard (D-Hawaii) also do not pay interns, according to the report. Swalwell’s office said it is looking at ways to change the policy; Gabbard’s said she will ­begin paying interns in 2019.

Outgoing Rep. Beto O’Rourke (D-Tex.), who lost his Senate bid against Ted Cruz (R-Tex.) last month, does not pay interns, the report said. His office did not respond to questions from The Post.

Mike DeBonis contributed to this report.