Joe Biden is the latest Democratic presidential candidate to target McDonald's in a bid to signal his concern for low-wage workers.

"We should unionize McDonald's," the former vice president told a gathering of McDonald's workers in Los Angeles on Thursday organized by Fight for $15, a union-backed group that pushes for a higher minimum wage. "I promise you, if I'm your next president, you'll never have had a better friend in the White House for working people and for unions than Joe Biden."

Pete Buttigieg, Amy Klobuchar, Bernie Sanders and Elizabeth Warren have all called on McDonald's to require its franchisees to do more to protect workers from harassment, while Cory Booker and former presidential contenders Kamala Harris and Beto O'Rourke this summer joined McDonald's workers rallying for higher pay in Las Vegas.

"The fight for 15 is about a lot more than $15 an hour ... this is about a fight for your dignity. You should be able to and we should unionize McDonald's" - Vice President @JoeBiden speaking to striking workers ahead of LA #DemDebate. #FightFor15 #UnionsForAll pic.twitter.com/qZVLVvwDsw — Fight For 15 (@fightfor15) December 19, 2019

Describing McDonald's as a "multibillion-dollar corporation" that exerts control over the work and rules at its restaurants, Biden described the demands for better pay and working conditions as "a fight for your dignity — it's not just the numbers."

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"Wall Street didn't build America, the middle class built America, and guess what, unions built the middle class," Biden declared. "We should unionize McDonald's."

Citing non-compete agreements that bar some low-income workers from moving to a competitor, Biden urged workers to continue their efforts to organize, saying Americans benefit when unions do well.

Reached for comment, McDonald's said the world's largest fast-food chain prides itself on building a supportive workplace. A spokeswoman also said the average starting pay at the chain's corporate-owned restaurants in the U.S. is more than $10 an hour, above the $7.25 federal minimum.

"McDonald's does not lobby against or participate in any activities opposing raising the minimum wage and believes elected leaders have a responsibility to set, debate and change mandated minimum wages," the spokeswoman said in an email.

McDonald's "recognizes the rights under the law of individual employees to choose to join — or choose not to join — labor organizations," she added.

McDonald's in March decided it would no longer lobby against hiking the minimum wage at the local, state or federal level. The decision marked a parting of ways with the National Restaurant Association, an industry trade group that long had McDonald's support in opposing any moves that would hike labor costs for its members.

A popular Main Street target for labor groups and the politicians who back them, McDonald's this week scored a major victory with a National Labor Relations Board ruling in favor of the company's franchise business model that places much responsibility for management decisions at the local franchise level and not corporate headquarters.