Lefty powerhouse duo Sen. Bernie Sanders and Rep. Alexandria Ocasio-Cortez headlined a rally outside Amazon’s JFK8’s warehouse on Staten Island on Sunday to show support for its workers’ newly formed union.

The pols’ appearance came as employees at Amazon’s LDJ5 warehouse, also on Staten Island, prepared to vote Monday on whether to unionize.

Ocasio-Cortez (D-Bronx) and Sanders (D-Vt.) took pot-shots at Amazon founder Jeff Bezos while urging the company to formally acknowledge the Staten Island union.

“We’ve got to recognize … that we have the first unionized Amazon in America right here in New York City,” AOC said.

She and Sanders also bemoaned Amazon’s controversial labor practices.

“I say to Jeff Bezos, who owns a $500 million yacht — I say, ‘Jeff, when you’re out on your yacht, I want you to think about the workers,’ ” Sanders said. “They want housing that is affordable. They want to be able to put away a few bucks to send their kids to college.

“They don’t want to be exploited and continue this massive turnover that takes place here because of the horrible working conditions.”