Rudy Giuliani doubled down on his claims that President Obama doesn’t “love America” in an interview with The Post Friday — claiming the commander-in-chief has been influenced by communists since his youth.

“From the time he was 9 years old, he was influenced by Frank Marshall Davis, who was a communist,” Giuliani said. The ex-mayor added that Obama’s grandfather introduced him to Davis, a writer and labor activist.

Giuliani also said another bad influence on Obama was Saul Alinsky, a community organizer whom the ex-mayor called a “socialist.”

The man once called “America’s mayor’’ also sharply criticized the president for having been a member of a church led by radical Chicago Rev. Jeremiah Wright.

“He spent 17 years in the church of Jeremiah Wright, and this is the guy who said ‘God damn America, not God bless America,’ ’’ Giuliani said.

“Obama never left that church.”

Giuliani said Obama doesn’t measure up to past presidents.

“He doesn’t talk about America the way John Kennedy and Ronald Reagan did, about America’s greatness and exceptionalism,” said Giuliani.

“He was educated by people who were critics of the US. And he has not been able to overcome those influences.”

Giuliani also implied he was the only one with the chutzpah to call out Obama, saying: “Somebody has to raise these issues with the president. Somebody has to have the courage to stand up.”

Giuliani also bashed Obama for seeming to focus more attention on the police shooting in Missouri, which, he said, “turned out to be justified,” than the killings by Islamic fanatics. “How could you hold a press conference about Ferguson and not hold a press conference when Christians and Jews were slaughtered?” he asked.

In a previous interview with The New York Times, Giuliani said his recent comments aren’t racist, because Obama was brought up by a “white mother” and went to “white schools.”

Referring to his claim that Obama doesn’t love America, Giuliani told The Post, “I don’t back off of that one bit.’’

Meanwhile, the White House countered by trying to make Giuliani seem less like a heroic guardian — and more like an oddball whom no one wants to be around.