On a scale of zero to 100, the ad's effectiveness never got above 20. It did not help that the ad was produced for Governor John Kasich, a candidate no one in the group supported.
"It was too far over the top," said one voter.
"They use every trick in the book to make him look like the ultimate bad guy," said another.
"It tried to make Trump look like the new Mussolini," said one more disgusted voter. "I mean, that ain't gonna happen."
Next up was a lengthy compilation of Trump's attacks on his fellow Republicans, over a pumping, distracting drumbeat. "He sweats more than any young person I've ever seen," said Trump of Senator Marco Rubio. Carly Fiorina talked like a "robot". Ben Carson was "pathological". Jeb Bush had "no money" and was "meeting with Mommy and Daddy" for support.
The dials turned higher - because the audience was laughing along with Trump. "It was like his greatest hits," said Tiffany Alm, 43, a stay-at-home mother who'd moved to the Washington area from Wisconsin. "It's Donald Trump, and it's entertaining."
Over three hours in Alexandria, Virginia, Luntz lobbed dozens of Trump-seeking missiles. All 29 in the group had voted for Mitt Romney in 2012. All either supported Trump, or had supported him earlier in the year.
To Luntz' amazement, hearing negative information about the candidate made the voters, only a few of whom gave their full names to the press, hug the candidate tighter.
"Normally, if I did this for a campaign, I'd have destroyed the candidate by this point," Luntz told reporters after the session. "After three hours of showing that stuff?"
With only two exceptions, the three hours of messaging, venting and friendly arguments revealed the roots of Trump's support.
Participants derided the mainstream media, accusing reporters of covering snippets of Trump quotes when the full context would have validated him. They cited news sources they trusted - Breitbart News was one example - to refute what they were being told.
"You know what Trump does?" said Teresa Collier, a 65-year old retiree. "He says something completely crazy, and I'm like: 'Oh, my God!' Then he dials back and starts explaining it, and saying how he'd do it, and it makes sense."
Only eight members of the group disagreed with Trump's proposal for a temporary ban on any Muslims entering the United States.
One of the holdouts said he was hosting an exchange student from Saudi Arabia, and did business in that country, but he could disagree with Trump about Muslims and vote for him anyway.
This voter listened as supporters of the plan explained that the media had lied about it, an argument furthered this week on conservative talk radio. As the night went on, the hold-out said he had become more likely to back Trump.
No one in the group wanted to find himself or herself on the side of the mainstream media - or of President Barack Obama.
When Luntz asked participants to sum Obama up in a word or phrase, "socialist" and "Jimmy Carter" tumbled forth, until one man raised the ante.
"I wouldn't urinate on him if he was on fire," he said.
"That's the meanest thing I've ever heard," said Luntz.
Frank Lanzillo, a 59-year old retired Marine, took that as a cue to explain just how anti-American the President really was.
"When you bend down to the Saudis, take your shoes off, put your hand on a Koran and then the Bible when you're sworn in?" Lanzillo said.
"He took his flag pin off. I'm a Marine and former deputy sheriff. He took that off, he was in the toilet to me," Lanzillo said. "I would not only not piss on him if he was on fire, I'd throw gas on him."
Lanzillo was referring to Obama briefly choosing not to wear a flag pin during the 2008 campaign. However, he was not sworn in on a Koran.
Asked if the President was a Christian, only three of the 29 participants raised their hands. Asked if he was born in the US, eight said no. When Luntz returned to policy, mistrust of the President informed the exclamations of trust in Trump.
"Donald Trump says that President Obama wants to allow 250,000 Syrian refugees to come into the country," said Luntz. "Who thinks that is mostly true?" Nearly every hand shot up.
"Do you know that Obama has said he wants only 10,000 refugees?" asked Luntz.
"What's in his heart?" asked one participant.
"He'd let as many in as possible," insisted another.
"It happens again and again," said Jeff Scrima, 38, who moved to the Washington area after serving as Mayor of Waukesha, Wisconsin. "The State Department says one thing, Obama says something else, and they change the policy to match him."
To Scrima and almost everyone else in the room, most criticisms of Trump broke down when they stopped to consider the source.
Trump had warned that political correctness was killing Americans. The shooting in San Bernardino, California, had proven him right.
One member of the group recalled angrily how the Texas administrators who had suspended a Muslim boy for bringing a strange-looking clock to school were demonised for simply being diligent.
Tiffany Alm shared what her family had heard on holiday in Paris, right after the terrorism of November 13.
"The news over there, the newspapers, they were interviewing Muslims," said Alm. "And they were saying they don't like America, they don't like France, but they're there. They say they won't become terrorists, but they hate America and France and Western culture."
Heads were nodding around the room.
"I've read the Koran," said Jeff Kelly, 57. "It says what it's purported to say. I know it says, you come across a non-Muslim, you kill him or convert him."
Luntz moved on to questions about Trump's claim that "thousands of Muslims" had "cheered the collapse of the World Trade Centre".
Almost no one doubted Trump; more than a few people wondered why this was controversial.
The youngest member of the group wondered why he never saw Muslims in the streets protesting about terrorism. Kelly said that there was fresh audio evidence of Muslims celebrating the San Bernardino shooting, though he could not immediately recall the source.
All that really mattered was that the Republican establishment had failed, badly, and that Trump was offering a way out. Asked whom they'd back in a three-way election between Rubio, Hillary Clinton and an independent Trump, just 10 said they would support the Republican nominee.
When Ted Cruz was swapped into the question, a bare majority - 15 - said they would stick with the party.
"The Republican establishment just had a heart attack," said Luntz.
Nothing seemed to budge the Trump voters. Almost all of them agreed that Clinton had committed crimes. Almost all agreed that the last Republican President had been wrong to invade Iraq in 2003.
Finally, Luntz asked for a thought experiment: To imagine incontrovertible proof that Clinton would win if Trump split the vote. Only then did the group agree to vote Republican over Trump.
"In that scenario, sure," said a middle-aged participant named Michael. "But that won't happen. Trump would win." That confidence only grew as Trump's alleged gaffes and mistakes were laid out.
At 6.30pm, when the session began, all 29 participants were asked to rate their likelihood of voting for Trump, and just 10 people said they were at nine or 10 out of 10. After one hour of mostly negative questions about Trump, six more people joined that confident group.
"I've been talking about negatives, and you're up on him!" said an astounded Luntz. "That's the story of Trump's poll numbers." Almost nothing was changing that picture.
The group heard Trump insist that the wives of the September 11, 2001, hijackers had been warned in advance and sent home. They saw Trump mock a New York Times reporter with a disability who had written about reports of post-September 11 celebrations. Some people winced; more of them rationalised what Trump had been saying.
"The real issue is that the reporter retracted his story after 14 years," said Scrima.
In three hours, the only issue that moved voters against Trump was one that evoked memories of the 2012 election. The group was shown an ad in which contractors blamed Trump for the loss of their jobs.
That, said one man, made Trump look less electable. He was downgrading the likelihood of his own Trump vote - from nine out of 10, to just eight.
"I can't wait for Iowa, because I now think Ted Cruz will win Iowa," said Luntz. "That will be a rallying cry. Losing there might actually help Trump win New Hampshire."
Media's extremist comparisons a double-edged sword
As we noted in the Washington Post on Tuesday after the Philadelphia Daily News labelled Trump "The New Furor" on its front page, the Republican presidential frontrunner has been drawing Hitler/Nazi/fascist comparisons for some time.
The New York Daily News, perhaps sensing that the trope is growing tired, went in a different direction on Wednesday, paraphrasing a famous poem by the Reverend Martin Niemoller:
When Trump came for the Mexicans,
I did not speak out - as I was not a Mexican.
When he came for the Muslims,
I did not speak out - as I was not a Muslim.
Then he came for me.
Niemoller's original goes like this:
First they came for the Communists,
And I did not speak out - because I was not a Communist.
Then they came for the Socialists,
And I did not speak out - because I was not a Socialist.
Then they came for the trade unionists,
And I did not speak out - because I was not a trade unionist.
Then they came for the Jews,
And I did not speak out - because I was not a Jew.
Then they came for me -
And there was no one left to speak out for me.
The text is all about Nazis. But wait, there's more! An accompanying cartoon depicts Trump wielding, in one hand, a sword that looks straight out of Aladdin and holding, in the other hand, the head of Lady Liberty, having apparently decapitated America's national symbol of freedom. So the imagery is pure Islamic State.
And the New York Daily News isn't the only one drawing parallels between Trump and the terrorist group that attacked Paris last month and apparently inspired last week's mass shooting in San Bernardino, California. On Comedy Central's The Daily Show on Tuesday night, host Trevor Noah declared that Trump is "white Isis", saying the real estate magnate is using a "radical ideology" to promote conflict between Islam and the West - just like the terrorists.
That, like Wednesday's tabloid cover, is over the top.
The Daily Show, clearly branded as satire, surely knows this, and I suspect that the Daily News does too.
They are making a rhetorical point - and a powerful one, at that.
But I wonder if it will have the desired effect, or perhaps the exact opposite.
The Trump haters who eat this stuff up already think he's a fascist with goofy hair, instead of a goofy moustache.
His supporters, however - who remain numerous if not growing in number - are galvanised when they see further evidence of what Trump has been telling them all along: The media is biased against me, it's us against them, and we are going to win.
