"Well, I know all those people very well," Trump said in an hour-long interview on Fox News' "Fox and Friends." "You remember I beat them all last time. I beat [Hillary] Clinton, I beat [Barack] Obama ... we've had many many successes and the big one is these are the same people I beat last time and they're not going to unite because they can't unite."

He added that Sanders is "very unhappy" over Biden, but "I call him 'Crazy Bernie' for a reason. You'll never make him happy."

But after show co-host Steve Doocy reminded Trump that Democrats are united because they want to beat him, the president turned his attacks to the "corrupt media," saying his biggest opponent isn't Biden or the Democrats, but the media. 

"Somebody like Biden, he doesn't know what to do," said Trump. "He doesn't come out because he can't. He doesn't take any questions from reporters. I keep saying to my people, here I am getting bombs thrown at me every day by people that are totally, you know, frankly dishonest reporters, but I'm getting, you know they are espousing the view of the radical left but here I am, bombs every day and every day and do a good job handling it."