At last week’s Republican debate, Carly Fiorina described a Planned Parenthood video showing “a fully formed fetus on the table, its heart beating, its legs kicking, while someone says, ‘We have to keep it alive to harvest its brain.’”

There is no such video . It does not exist . This pesky detail has since touched off a striking series of events.

First, the GOP candidate insisted the day after the debate that she “didn’t misspeak,” adding, “I have seen those images.” Of course, Fiorina couldn’t have seen those images, because there are no such images.

Later, Vox’s Sarah Kliff asked the Fiorina campaign to back up her claim with evidence. The Republican staffers tried, but failed , to substantiate the claims. Even the right-wing group that released the videos can’t bolster the Republican presidential hopeful.

Yesterday, Fiorina appeared on “Fox News Sunday,” where host Chris Wallace tried to lead Fiorina to acknowledge reality. From the Nexis transcript:

WALLACE: First of all, do you acknowledge what every fact checker has found, that as horrific as that scene is, it was only described on the video by someone who claimed to have seen it? There is no actual footage of the incident that you just mentioned? FIORINA: No, I don’t accept that at all. I’ve seen the footage. And I find it amazing, actually, that all these supposed fact-checkers in the mainstream media claim this doesn’t exist. They’re trying to attack the authenticity of the videotape.

Actually, they’re not. The fact-checkers examined Fiorina’s claim and concluded that it’s the opposite of reality. Offered multiple opportunities to substantiate the claim with evidence, Fiorina and her aides have offered nothing. The authenticity of the tapes is a separate question altogether.

The more the Republican says, “I’ve seen the footage,” the more we’re reminded there is no such footage.

Americans can learn a lot about presidential candidates by reviewing their records and proposals, but how they respond to challenges tells us something important, too. In this case, a candidate for national office was caught saying something that was plainly untrue, which in turn created a test of sorts. How would Carly Fiorina defend a lie? What would her defense tell us about her readiness for national office?

The answers so far should be alarming for her campaign supporters.

TPM’s Josh Marshall added the other day, “Fiorina has a habit of simply making things up. In the case of the parts of the Planned Parenthood videos, the way she made it up seems to verge on the pathological. Again she says she saw something in these videos that completely wasn’t there.”

The L.A. Times’ Michael Hiltzik concluded that “it’s time for Carly Fiorina to apologize to Planned Parenthood.” I suspect that won’t happen, though it’d be a more coherent response than the one the candidate has offered thus far.