Donald Trump's list of potential running mates has been whittled down to as few as four candidates, said the presumptive Republican nominee's former campaign manager on Thursday.

"The list, when I left, was very very short," said Corey Lewandowski, whose whirlwind week has seen him fired from the businessman's campaign and then picked up by CNN to be a political commentator. "It was ongoing conversations. The individuals who he is talking to about being part of that process have all agreed that they want to be part of that process."

"It's no more than four individuals right now," he told CNN's Erin Burnett, but did not go as far as to mention names. He did say that these individuals are "the absolute best," and are people that "everyone will know."

Lewandowski also denied what he called "speculation" that people considered for the vice presidential spot are not interested in the job.

"They want to do this," Lewandowski said.

Earlier Thursday, Trump admitted that Arkansas Sen. Tom Cotton and New Jersey Gov. Chris Christie, while not guaranteed for a VP pick, are "high on the list" for posts in a Trump administration.