||"They hired people. They paid them $1,500, and they're on tape saying be violent, cause fights, do bad things," Trump said on the debate stage Wednesday night, referencing the video by O'Keefe.
NBC News has not corroborated the video.
The payment was first reported by Think Progress and was listed in a compilation of donations the Trump Foundation gave to the Washington Post.
"I was wondering what happened with my rally in Chicago and other rallies where we had such violence. She's the one and Obama that caused the violence," Trump said at the debate.
O'Keefe has produced numerous videos that have attempted to take down members of the media, Democrats or progressives. He led the undercover videos during the 2008 election of progressive group ACORN and of NPR executives calling tea party members "racist."
Breitbart is the platform where O'Keefe's videos are posted. The former head of Breitbart, Steve Bannon, is the CEO of Trump's campaign.