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"What the hell has he done for the African-Americans?" Trump asked

Later, Trump pledged to visit Philadelphia and speak to the black community

Manassas, Virginia CNN  — 

GOP presidential front-runner Donald Trump ramped up his criticism of Democrats at a Wednesday night rally, previewing potential general election attacks as he seeks to broaden his appeal.

Trump cited the high unemployment rate among African-American youth, and said pledged to do more for African-Americans than President Barack Obama.

“What the hell has he done for the African-Americans?” Trump asked of the country’s first black president. “He’s done nothing. I don’t think he cares about them. He’s done nothing.”

Later, Trump pledged to visit Philadelphia and speak to the black community. He was responding to a question from a black pastor in the audience, who Trump had earlier brought on stage. The Philadelphia-based pastor, T. Milton Street, asked Trump if he would come to Philadelphia and talk about his plan to address “black-on-black crime.”

“I would do that,” Trump said, noting he went to University of Pennsylvania’s business school in Philadelphia. “The answer is yes.”

While he was on a roll hitting his GOP opponents with the usual attacks, including calling former Florida Gov. Jeb Bush “low energy,” Trump also looked ahead to his likely general election opponent, Democratic front-runner Hillary Clinton.

“She’ll do an event like this and they won’t show up for like five – you know why, she goes home and sleeps,” Trump said, saying Clinton neither has the “strength” nor “stamina” to be president.

“We shouldn’t be laughing we should be crying, because she’s the front-runner,” he told the crowd.

He returned to the jab at the end of his speech.

“Unlike Hillary, I don’t go to sleep, I think about things,” Trump said. “Hillary goes to sleep and then you don’t see her for five days.”