Rudy Giuliani was attacked by a worker at a ShopRite on Staten Island on Sunday while campaigning for his son, leaving the 78-year-old former New York City mayor shaken, witnesses and law-enforcement sources said.

Giuliani told The Post he almost went down when he was hit but regained his composure — even as his attacker kept cursing at him…

“I was shoulder-to-shoulder with Rudy inside ShopRite,” Rugova-Johnson said. “We’re talking, and all of a sudden an employee came out of nowhere and open-handedly slapped him in the back and said, ‘Hey, what’s up scumbag?’

“[The attacker] was on duty at the time,” the witness said. “The cops arrested him.”