On MSNBC's "The Last Word" with Lawrence O'Donnell, NBC national affairs analyst John Heilemann explained what could be learned from Trump's demeanor during a rambling press conference at the United Nations.

"John Heilemann, who is the Donald Trump who you saw today at the United Nations?" O'Donnell asked. "That was a lifeless Donald Trump at the United Nations."

"I think deflated," Heilemann replied.

"And if not wholly defeated yet, Lawrence, I think you started to see signs of what a defeated Donald Trump would look like," he continued. "Today he seemed limp -- as if the air had been kind of taken out.

"I keep saying deflated. He looked a bit like a beaten dog today -- and that’s a little bit mean to dogs," Heilemann said.

"I think if you start to think about where this could go, that’s the Donald Trump I think you’ll be seeing more and more as this thing encroaches further and further onto his political capital, as his approve rating falls further and further, as his base starts to erode, and I think to Mike’s point, when the numbers start to get to the point where Republicans -- just doing the straight math -- look at Donald Trump and he’s more of a liability than an asset and they start to abandon him, that day will come," he explained.