Analysis by Chris Cillizza, CNN Editor-at-large

(CNN) -- The goal of politicians appearing on Sunday shows is simple: Set the agenda for the week ahead.

Rudy Giuliani achieved that -- and then some -- in an appearance on "Meet the Press" on Sunday. But the agenda he set was an absolute disaster for the Trump White House. Watching it was the equivalent of watching someone slip on a banana peel on the street -- it's hilarious and sad all at once. You feel bad for laughing but you find yourself laughing anyway. (And then you realize you may just be crying).

Let's start with Giuliani's seeming attempt to rebut the idea of truth. Here's the back and forth with "MTP" host Chuck Todd -- begun when Todd asks Giuliani why President Donald Trump couldn't simply sit down with special counsel Robert Mueller and tell the full truth:

GIULIANI: And when you tell me that, you know, he should testify because he's going to tell the truth and he shouldn't worry, well that's so silly because it's somebody's version of the truth. Not the truth. He didn't have a, a conversation --

CHUCK TODD: Truth is truth. I don't mean to go like --

RUDY GIULIANI: No, it isn't truth. Truth isn't truth. The President of the United States says, "I didn't -- "

What Giuliani is, I think, trying to say is that not everything that Mueller might ask about is a fact. The example he cites is how former FBI Director James Comey has said that Trump asked him to leave off the investigation into former national security adviser Michael Flynn while Trump has insisted no such conversation took place.

"Donald Trump says, 'I didn't talk about Flynn with Comey,'" Giuliani noted. "Comey says, 'You did talk about it,' so tell me what the truth is."

OK, a few things here.

First, the idea that the fact that Trump would describe a meeting with Comey differently than Comey has isn't perjury -- as Giuliani would like you to believe. It's a "he said, he said" -- which happens all the time in a court of law. So the idea that Trump can't talk to Mueller because it's possible he had a differing understanding of what he told Comey is a red herring.

Second, not all "he said, she said" situations are created equal. Comey testified under oath -- in written testimony to the Senate Intelligence Committee -- that "[Trump] asked what we could do to 'lift the cloud.'" Trump saying -- or tweeting -- that he never mentioned the idea of going easy on Flynn is entirely different. He's not under oath. He can say almost whatever he wants. And Giuliani's assertion that Trump would tell Mueller exactly what he has said publicly is, again, sort of a misdirection. Saying what you would tell the special counsel is not the same thing as actually sitting down with the special counsel.

Third -- and this one feels obvious -- you can't, ever, say "truth isn't truth." That goes double when you are part of an administration that has already used the phrase "alternative facts." And it goes triple when you represent a President who, in the last month, has said "don't believe the crap you see from these people, the fake news. ... What you're seeing and what you're reading is not what's happening."

Like Todd said, truth is truth. Facts are not up for debate.

Giuliani, clearly being leaned on to fix the mess he made, tweeted out a clarification on Monday morning.

"My statement was not meant as a pontification on moral theology but one referring to the situation where two people make precisely contradictory statements, the classic 'he said, she said' puzzle," Giuliani tweeted. "Sometimes further inquiry can reveal the truth other times it doesn't." (Say it with me: Perjury isn't "he said, she said.")

If Giuliani had only said "truth isn't truth," that would have been bad enough. But he did more! Way more!

Here's Giuliani and Todd talking about the June 2016 Trump Tower meeting between the campaign's senior officials and a group of Russians:

GIULIANI: Well, because the meeting was originally for the purpose of getting information about, about Clinton. The meeting turned into a meeting --

CHUCK TODD: Which in itself it's attempted collusion. I understand --

RUDY GIULIANI: No it's not.

CHUCK TODD: You just said it. The meeting was intended to get dirt on Hillary Clinton from a criminal lawyer.

RUDY GIULIANI: No, it wasn't. No, no.

CHUCK TODD: That was the intention of the meeting, you just said it.

RUDY GIULIANI: That was the original intention of the meeting. It turned out to be a meeting about another subject and it was not pursued at all. And, of course, any meeting with regard to getting information on your opponent is something any candidate's staff would take. If someone said, I have information about your opponent, you would take that meeting. If it happens to be a person with a Russian --

CHUCK TODD: From the Russian government?

RUDY GIULIANI: She didn't represent the Russian government, she's a private citizen. I don't even know if they knew she was Russian at the time. All they had was her name.

There's so much here; it's such a rich text.

First: Giuliani says the intention of the meeting was "for the purpose of getting information about, about Clinton." Then, when Todd puts out that such a deal could well amount to collusion, Giuliani say that the meeting was not, in fact, intended to get dirt on Clinton. Uh......so, like, the thing you said literally two sentences ago was not true? This is the new true thing?

OK.

Now onto this claim about what Donald Trump Jr., Paul Manafort and Jared Kushner knew going into the meeting. "I don't even know if they knew she was Russian at the time. All they had was her name," Giuliani said of Russian lawyer Natalia Veselnitskaya.

Nope! In an email from music publicist Rob Goldstone, who was functioning as a liaison for Russian billionaire Aras Alagarov to Don Jr., Goldstone wrote:

"The Crown prosecutor of Russia met with his father Aras this morning and in their meeting offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father.

"This is obviously very high level and sensitive information but is part of Russia and its government's support for Mr. Trump - helped along by Aras and Emin."

You could make the argument that Kushner and Manafort might not have known the details of the meeting -- and that it was with Russians -- prior to sitting down. It is impossible to make that argument about Don Jr.

Impossible.

Here's the thing: The sole reason Giuliani is out on these Sunday shows is because the President likes the job he is doing. And we know from lots and lots of evidence that Donald Trump is not terribly concerned with the truth; he is far more interested in his advocates going out and fighting for him.

But even by Trump's odd standards of success, what Giuliani did on Sunday was a total train wreck. Let's see if Trump allows Giuliani to have a do-over. Trump allies should hope he doesn't.