Shortly before November’s midterm elections I interviewed a Donald Trump supporter, coming out of a debate between three local candidates in a congressional race, asking how she felt about the president’s attitude to women. “I need to see the facts and the actual documentation,” she said. “I can’t just do all this hearsay.”

“What about when he says he personally grabs women and kisses them,” I prodded. “That was him saying that.”

“I have not personally seen him do that,” she said.

“But he said it though,” I insisted.

“I haven’t seen it. I haven’t heard it for myself.”

Here was a woman who went to local debates, offered chapter and verse on the evils of Obamacare and was studiously following the progress of the caravan of migrants and asylum seekers heading for the southern border. I have no way of knowing for sure if she’d heard one of the most famous audio clips ever recorded or not. But the narrowly tailored nature of her determined denial itself spoke volumes.

Trump supporters long ago decided to discount, dismiss, disbelieve, indulge, ignore, endorse, excuse or otherwise rationalise his appalling behaviour. Evidence of sexual harassment, misogyny, bigotry and lying were all fully apparent when they put him in the White House. Back then 81% of white evangelicals voted for the man who had five children from three different women (imagine for a second what they would have made of Barack Obama if he’d had that kind of personal life). Since then we have learned that Trump had an affair with a Playboy model a few months after his third wife gave birth to their son, and then cheated on both of them with a porn actor. Today 71% of white evangelicals still support him. It’s not that his base don’t know. It’s that they have found a way not to care.

So when Trump’s former lawyer, Michael Cohen, calls him a “racist” a “cheat” and a “conman” during testimony before Congress yesterday, don’t expect normal rules to apply. It is unprecedented for a man who was so recently so close to a sitting president to be this scathing during an ongoing investigation. There may yet be legal ramifications. However, since Cohen insisted he had no evidence of collusion with Russia, this was mainly a must-see news event: compelling theatre with complex characters. Politically it is unlikely to make much of a difference. Much of what he said either was presumed, was known, won’t be believed or will be selectively unheard. Cohen has lied to Congress, and pretty much everywhere else, before. This is his contrition tour before he starts a three-year prison sentence for, among other things, fraud. Trump supporters who dismiss him on that basis should bear in mind that he was lying for his boss – Trump.

For those who are interested, Cohen illustrated what an emotionally, morally and socially stunted little man America has for a president. He recounted how Trump took money from his own charity and ordered a fake bidder to buy a picture of himself at an inflated price in a auction of celebrity portraits so that his would be the most expensive. Then he tweeted his surprise. “Just found out that at a charity auction of celebrity portraits in E. Hampton, my portrait by artist William Quigley topped list at $60K.”

He threatened his high school and college with legal action if they ever released his grades or test scores. This man is not merely thin-skinned. He is translucent.

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It won’t upset most of Trump’s base that he believes black people are too stupid to vote for him, asked Cohen if he could name a country run by a black person that wasn’t a shithole, and remarked, when driving through an impoverished neighbourhood of Chicago, “only black people can live that way”. That’s what they like about him. But there are other things Cohen said that should worry a base dominated by veterans and small business owners. Trump “revelled” in news that he routinely underpaid or refused to pay businesses that provided services for him. Regarding his medical deferment for Vietnam he told Cohen: “You think I’m stupid? I wasn’t going to Vietnam.”

But the most telling part of Cohen’s testimony was when he explained Trump’s motivation for running in the first place. “Donald Trump is a man who ran for office to make his brand great … He would often say this campaign was going to be the greatest infomercial in political history.”

The presidency was never the point. He had no idea that the political establishment would be so craven and career politicians be so inept that he might prevail. “He never expected to win the primary. He never expected to win the general election. The campaign – for him – was always a marketing opportunity.”

Projection and image-management has always been a feature of American politics. That’s how Ronald Reagan became the small government president who actually doubled the national debt; Bill Clinton was the “first black president” who oversaw a huge increase in black incarceration; George Bush Jr was the war president who people would like to have a drink with even though he was a teetotaller who dodged the draft, and Obama was black America’s favourite president who presided over a widening of the wealth gap between black and white. But they were politicians being marketed with a view to gaining power. If we believe Cohen on this score, Trump is a businessman marketing himself with a view solely to self-promotion, who ended up in power by accident.

As Naomi Klein points out in No is Not Enough, the answer to the question of why he can commit scandal after scandal and tell lie after lie and yet press on apparently unscathed (the issue of paying hush money to keep his mistress quiet is a campaign finance matter – most shrug at the infidelity) is embedded in the nature of the image he has crafted. “His brand is in being the ultimate boss, the guy who is so rich he can do whatever he wants, whenever he wants and to whomever he wants (including grabbing whichever woman he wants by whichever body part he wants) … According to these rules you don’t need to be objectively good or decent, you only have to be true and consistent to the brand you have created.”

This says a great deal about the state of American politics, but for now let’s just concentrate on two aspects. First, an election can be regarded not as a battle of ideas, agendas or even personalities, but as a marketing opportunity. There’s so much money sloshing around and so little expected in terms of substance that they might as well be selling soap. Second, this is the brand that won. The brand of a racist, a conman and a cheat.

• Gary Younge is a Guardian columnist