NEW YORK — Vice President Joe Biden said he is overwhelmed at times by his son’s death and unconvinced he could commit fully to being president, in an emotional interview that cast a deep pall over his deliberations about the 2016 presidential race.

Asked about his 2016 decision on CBS’ “The Late Show,” Biden said Thursday he’d be lying if he said he knew he was prepared to run following Beau Biden’s death in May to brain cancer. With a level of candor seen rarely in politics, he recalled a breakdown of his emotions during a recent visit to a Colorado military base when a well-wisher yelled out the name of his son and referenced his decorated military service in Iraq.

“All of a sudden, I lost it,” Biden said. “How could you — that’s not — I shouldn’t be saying this: You can’t do that.”

Biden’s much-anticipated appearance on “The Late Show with Stephen Colbert” was expected to take on a light and comedic tone, but instead veered almost immediately into raw and personal territory. He said White House hopefuls must be able to promise voters they can commit their whole heart, soul, energy and passion, and said, “I’d be lying if I said that I knew I was there.”

“Nobody has a right, in my view, to seek that office unless they’re willing to give it 110 percent of who they are. And I am, as I said, I’m optimistic, I’m positive about where we’re going,” Biden told Colbert. “But I find myself — you understand it — sometimes it just overwhelms you.”

Since his son’s death, Biden has frequently peppered his speeches with references to Beau and the impressive resume he developed in his 46 years. Yet Biden went further in the interview, describing in detail conversations he had with Beau in the months before his death at a military hospital.

“He said, ‘Dad, sit down, I want to talk to you.’ He said, ‘Dad, I know how much you love me,”’ Biden recalled. “Promise me you’ll be all right, because no matter what happens, I’m going to be all right.”

If Biden seemed unusually willing to bare his soul, it may have been due to his host. Colbert lost his father and two brothers in a plane crash as a child.