Bernie Sanders to visit unionizing workers at Amazon and Starbucks

The details: Earlier this month, Amazon workers at a Staten Island warehouse voted in favor of forming a union, a victory that is expected to spur union growth around the country.

• Starbucks employees at stores across the country — including Atlanta, Seattle, Philadelphia, Minnesota and New York — have made moves to unionize since the start of this year alone.

What they're saying: "The workers @amazonlabor are taking on one of the most powerful companies in the world and one of the wealthiest men in America. I’m proud to stand in solidarity with them and support their fight for dignity on the job. See you on Sunday!" Sanders tweeted Wednesday.

• On Tuesday, Sanders responded to a tweet celebrating a Richmond Starbucks store's vote to unionize, writing, "The movement of workers demanding dignity on the job wins again!"

• "Congratulations to Starbucks workers in Richmond on your vote to unionize! I will see you Sunday!" he added.

Sanders was announced to attend the event in Richmond — a Unity Fest organized by Starbucks Workers United — last month.

• Christian Smalls, president of the Amazon Labor Union (ALU), announced Sanders' Sunday visit in a tweet earlier Wednesday.

Go deeper: Why there's been a surge in unionizing efforts