They all seem to be perfectly reasonable American voters: The housewife ironing as she calls Donald Trump "authentic," the house painter who lauds Trump's job creation, the earnest citizen who calls him a "winner." The problem? The housewife is ironing a hooded Ku Klux Klan sheet, the painter is painting "White Power" on a house, and Joe Citizen is wearing a Nazi arm band.

The spoof ad featured on Saturday Night Live and sponsored by "Racists for Trump" played to great gasps and guffaws among the New York studio audience for the TV programme over the weekend.

But it is part of a building social network and media buzz comparing Trump to Adolf Hitler after Trump recently dodged condemning former grand wizard of the KKK David Duke after Duke endorsed him.

Comedian Louis CK, who called Trump a "dangerous, insane bigot", pleaded with his fellow Yanks shortly before the SNL ad in an almost panicky email: "Please stop it with voting for Trump. It was funny for a little while. But the guy is Hitler. And by that I mean that we are being Germany in the '30s. Do you think they saw the sh*t coming? Hitler was just some hilarious and refreshing dude with a weird combover who would say anything at all."

He added: "If you are a true conservative. Don't vote for Trump. He is not one of you. He is one of him. He is playing you. He's the worst of all of us. He's a symptom to a problem that is very real. But don't vote for your own cancer. You're better than that."

He said he "gets" the obsession with Trump among a populace sick to death of the their politicians — and that voting for him is a kind of "national suicide" revenge. Trump is also so provocative that he's addictive, the comedian acknowledged: "I mean I can't wait to read about Trump every day. It's a rush. But you have to know this is not healthy."

Louis CK is joining a chorus of critics (and memes) making the Hitler connection.

Earlier Bill Maher on HBO's Real Time cited a press clipping that Trump "kept a volume of Hitler's speeches by his bedside." Said Maher: "I think this tells us a lot about where Donald Trump is getting his ideas."

Trump himself provided a chilling visual of a Nazi salute when he asked supporters at a Florida rally to raise their right hands in the air to swear allegiance to him. "Don't forget you all raised your hand, you swore," Trumps said to the crowd. "Bad things happen if you don't live up to what you just did."

The comparison began far earlier on social networking sites with memes featuring Trump with a Hitler moustache, and comparing Trump and Hitler's positions of blaming immigrants for their nations' problems and vowing to bar them.

The buzz grew louder after Trump hem and hawed in a CNN interview when asked about his reaction to an endorsement by David Duke, whom he professed not to know, and the KKK. He later blamed a faulty network earpiece, though he clearly repeated David Duke's name. He called him a "Klansman" in 2002.