(CNN) In defending President Donald Trump's comments to the widow of a slain soldier, White House Chief of Staff John Kelly on Thursday undercut a stunning allegation levied by Trump against a member of Congress a day earlier.

On Wednesday morning, as the controversy over his call to the wife of Sgt. La David Johnson widened, Trump accused Rep. Frederica Wilson, a Florida Democrat, of lying about the details of the conversation -- in which he reportedly told Myeshia Johnson of her husband, "he knew what he signed up for, but I guess it still hurt."

Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof). Sad! — Donald J. Trump (@realDonaldTrump) October 18, 2017

"Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof)," Trump tweeted. "Sad!"

But there was no clear-cut evidence, like a recording, as White House Press Secretary Sarah Sanders conceded on Wednesday after being pressed for details by CNN's Sara Murray -- only a handful of witnesses. One of them, she said, was Kelly. A day later, the chief of staff, who lost his own son in combat in Afghanistan, took the podium to provide new context.

Kelly spoke at length, and in detail, about what follows the death of a US soldier at war -- and the painstaking, awful banality of how the government delivers the news to their loved ones. He talked about his own experience and told reporters that Trump tried his level best to communicate warmly, with empathy, in his own calls.

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