Addressing a packed crowd at a convention center and joined on stage by his wife, Melania, for the first time on the campaign trail, a fiery Trump linked Obama's presidency to the protests and unrest over racial discrimination and policing that have seized cities like Baltimore and Ferguson, Missouri.
"Look at our inner cities," Trump said before listing several cities where protests have broken out over tensions between police and minority communities. "I call him the great divider. I am going to be a unifier."
The Republican front-runner's comments come as he's stoked controversy in recent days by shining a spotlight on Muslims in the wake of the Paris terror attacks, raised dubious claims about the 9/11 attacks and justified the beating of a Black Lives Matter protester at a rally this weekend.
Trump again called that protester "obnoxious," several days after he suggested the black protester who was punched and kicked by a half-dozen white attendees at a Saturday rally "maybe should have been roughed up."
Over the last week, Trump has indicated he would establish a database of all Muslims living in the U.S. and has floated the idea either shutting down some U.S. mosques or at least surveilling mosques to guard against terrorist plots.
"There's some nastiness, there's some meanness there. There's something going on in the mosques and other places," Trump said Tuesday, before asking why Obama "is so emphatic on not solving the problem?"
"There's something we don't know about. There's something we don't know about," Trump said, before someone in the audience shouted, "He's a Muslim!"
Trump also called on Americans to take action and report suspicious activity in their neighborhoods.
"The real greatest resource is all of you, because you have all those eyes and you see what's happening. People move into a house a block down the road, you know who's going in. You can see and you report them to the local police," Trump said.
"You're pretty smart, right? We know if there's something going, report 'em. Most likely you'll be wrong, but that's OK. But let the local police go in and check out and you get rid of this stuff. That's the best way. Everybody's their own cop in a way, you gotta do it. You gotta do it," he said.
Trump also again claimed that "thousands" of Muslims in New Jersey celebrated the terrorist attacks of 9/11, though it has been widely debunked by fact checkers.
Trump's supporters roared in approval at the mention of each of those lines in Trump's speech.
Trump had the crowd's attention from start to finish, beginning by calling up his wife and three of his children to join him on stage.
"He will be the best president ever. We love you," said Melania Trump, in her first remarks on the campaign trail.
His supporters also erupted into applause when Trump again called for reestablishing the practice of waterboarding in questioning terror suspects. On Tuesday he said the practice, which is considered torture by international conventions, delivered al-Qaeda's now deceased leader to the U.S.
"We would not have gotten Osama bin-Laden -- from what I hear -- without waterboarding," Trump said.
The CIA has claimed the method was effective in helping interrogators draw information from 9/11 mastermind Khalid Sheikh Mohammed.
But a Senate Intelligence Committee report
released last December on the CIA's use of "enhanced interrogation techniques" such as waterboarding determined the practice was largely ineffective and resulted in false and fabricated confessions and information.
Trump suggested the U.S. should reinstate waterboarding because of ISIS's brutality -- which Trump said pales in comparison to the simulated drowning.
"I'm going to be the best protector. I'm going to fight like hell for this country," Trump said.