WATCH: Jake Tapper wonders why Sarah Huckabee Sanders picked today to lie less to reporters over Trump N-word flap

On Tuesday, panelists on CNN's the Lead with Jake Tapper tried to make sense of White House Press Secretary Sarah Huckabee's refusal to guarantee that President Donald Trump has never said the N-word.

Asked repeatedly by reporters if she was willing to concretely say that no tape of President Donald Trump using the N-word in any context exists, Sanders equivocated.

"I can't guarantee anything," she said.

Jake Tapper observed that it seems that for once, Sanders seemed to be telling the truth. "First of all, I think it's stunning that .. today was the day of all days where she decided lying was something she wasn't willing to do," he joked.

"But the idea that you can't make that guarantee ... why can't you make that guarantee?" Tapper wondered.

Karine Jean-Pierre, a senior advisor with MoveOn.org, pointed out that no one should be surprised if such a tape turned up.

"If you don't know that Donald Trump isn't a racist then you haven't been paying attention.  ... " she noted. "Just look at his Twitter!"

WATCH: