Current and former Walmart workers protested at the Brooklyn headquarters of Hillary Clinton's presidential campaign Wednesday, calling on Clinton to address Walmart's pay and labor practices and noting her "long-standing ties" to the company, where she served as a board member from 1986 to 1992.

The protest came a day after the Service Employees International Union, a powerhouse in the labor movement and backer of the Fight For $15 minimum wage campaign, officially endorsed Clinton for president. While Clinton has spoken in support of a $12 minimum federal hourly wage, she has stopped short of calling for the $15 minimum that is becoming a widespread demand among labor activists.

After a heated exchange with security in the building lobby, the protesters — including seven who are fasting as part of a national hunger strike against the retailer — had an impromptu sidewalk meeting with Clinton campaign labor outreach director Nikki Budzinski.

"I hear you. We hear you," she told the group. "We know this is an important issue."

Initially, building management asked the workers to leave the lobby and threatened to call the police, before eventually agreeing to deliver a letter signed by the fasting workers to the campaign offices.

"This week, in NYC, and across the country... [we] are fasting for $15 an hour and full-time, predictable schedules," the workers wrote. "Instead of hiding our hunger and hiding the reality of skipping meals, we are taking our struggles with food insecurity public.

"We all need our country's largest employer to set a new standard, and we need you to lead," read the letter, addressed to Clinton. The workers specifically asked for a meeting with Clinton and for her to publicly call on Walmart to raise pay and provide more predictable schedules.