John Kelly, President Trump's former chief of staff, says if the Senate doesn't call new witnesses in the impeachment trial, it will have only done "half" of its job.

Kelly spoke in an interview with NJ Advance Media on Friday as the Senate appeared poised to reject additional witnesses in the trial, and he suggested this would be a mistake.

"In my view, they kind of leave themselves open to a lot of criticism," Kelly said, going on to add that "if I was advising the United States Senate, I would say, 'If you don’t respond to 75 percent of the American voters and have witnesses, it's a job only half done. You open yourself up forever as a Senate that shirks its responsibilities."

The 75 percent statistic refers to a recent Quinnipiac poll, which found that 75 percent of registered voters think witnesses should be allowed to testify in the impeachment trial, including 49 percent of Republicans.

Kelly also said in the interview, "It seems it was half a trial."

These comments from Trump's former chief of staff came days after he spoke out in defense of claims made in former National Security Adviser John Bolton's book that Trump tied Ukraine aid to investigations into Democrats. "If John Bolton says that in the book, I believe John Bolton," Kelly said. Kelly again supported Bolton Friday, saying he's a "copious note taker" and "an honest guy."

Shortly after Kelly's comments were published, House Intelligence Committee Chair Adam Schiff (D-Calif.) was already citing them in the impeachment trial, responding to Kelly's "half a trial" comment by saying on the Senate floor, "I can't agree. A trial without witnesses is no trial at all." Brendan Morrow