Donald Trump is a stone-cold racist. There was surely no doubt about that, not after he launched his presidential campaign by branding Mexican migrants as rapists and criminals. Or after he praised the white supremacists who marched under swastika banners in Charlottesville as “very fine people”.

Or after he talked of migrants from Nigeria returning to their “huts”. Or suggested all Haitian newcomers to the US had Aids. Or after he called black players in the National Football League “sons of bitches”. Or after he claimed that America’s first black president was really born in Africa – and demanded to see his university papers, because he didn’t believe he was smart enough to get into Harvard.

So nobody can say they are surprised that, in the course of an Oval Office meeting on Thursday, Trump suggested the US should no longer take in immigrants from “shithole countries” such as the nations of Africa, but look instead to the likes of Norway. That’s how racists see the world: black countries are worthless, while the only acceptable foreigners hail from a land of supposed Nordic purity.

You can be disgusted and outraged, but you can’t be surprised. We know Trump is a racist with the same iron certainty with which we know Trump is a misogynist. This, after all, is the man who was caught on tape boasting of a modus operandi with women that amounted to sexual assault. Who said of one female TV anchor who’d crossed him that she had “blood coming out of her wherever”. Who once sent a note to a female columnist, calling her a “dog” and adding that she had “the face of a pig”. Who during the 2016 campaign dismissed Republican rival Carly Fiorina on the grounds that no one would vote for “that face”.

Given all that, what could be sweeter or more delicious than seeing Trump beaten in 2020 by a woman – and by a black woman at that? The humiliation would be total.

It would be satisfying indeed to see Winfrey challenge a man who is not just a racist but a coward and a liar

Which is surely one reason why even the hint that Oprah Winfrey might run for president has generated such instant excitement. Her speech at last weekend’s Golden Globes ceremony may not have been intended as a campaign launch, but the manner of its delivery – rousing and intensely political – firmly planted that thought. Her own partner did nothing to put out the fire when he said that same evening: “She would absolutely do it.”

We know the anguish it would cause Trump to face Oprah on that debate stage, confronting a black woman whose success is so much greater than his. For one thing, she is self-made. While he started out with what he called a “small loan” of $14m from his property developer father, Winfrey began life in rural Mississippi as the descendant of slaves and the daughter of a teenage single mother who worked as a housemaid.

Trump had a good run as the frontman for a single TV series, The Apprentice. Winfrey has been a fixture of American TV for more than three decades. Her billions are real, his are shaky. Her record of philanthropy is serious. His has been exposed as bogus.

The contrast between the two would be unforgiving. She is trusted and, having taken on a clutch of difficult subjects – she was an early advocate for victims of child abuse, speaking about her own experience of being raped at the age of nine – she has moral authority.

Politically, she would be likely to energise core constituencies, including the African-American voters who did so much to propel Barack Obama into the White House in 2008 and 2012, but who turned out in smaller numbers for Hillary Clinton. Winfrey clearly has a following among white women, a group that overall backed Trump.

So it would be satisfying indeed to see Winfrey challenge a man who, on Thursday alone, reminded us that he’s not just a racist but also a coward and a liar. Those latter two attributes were compressed into a single tweet as Trump announced he would not, after all, be coming to London next month to open the new US embassy.

Clearly too scared to face the hordes of protesters who would have greeted him, he made up some laughable – and mendacious – excuse about opposition to the “bad deal” Obama had made in selling off the old embassy building. That move was actually announced in October 2008, when Obama was a mere candidate and George W Bush was president.

And yet, no matter how enticing the prospect of seeing Trump confronted by a black woman who is his superior in every way, I’m not sure I want Oprah Winfrey to run for president. And it’s not because I don’t think she might win.

My worry is that a Trump v Winfrey contest would confirm that the Trump era was no aberration, but a new normal. It would say that, from now on, the US presidency is a celebrity post, open only to those who have found spectacular fame, usually via television. Presidential elections inevitably include an element of the popularity contest, but if the next one is The Apprentice v Oprah, then a future beckons in which all such elections will be nothing but.

Even if he lost in 2020, a battle against Oprah would not be a defeat of Trumpism but a perverse vindication of it. For what connects the multiple failings of this president? The common thread, besides Trump’s racism, bigotry and featherbedding of the rich, is his disdain for evidence and his contempt for the norms and practices of good governance.

Trump’s campaign for the presidency rested on an insistence that none of those things mattered: that fame, wealth and gut instincts were enough. If Democrats nominate Oprah for the White House, they would, in effect, be declaring that Trump was right, that the presidency is indeed an extension of the entertainment industry: they’d just want to install a different entertainer.

Democrats need to make a better argument than that. Yes, they need to find a candidate who can rouse the passions and stir the faithful, as Obama did, Hillary couldn’t and perhaps Oprah might. But they also need to persuade American voters that political experience matters; that the highest decisions of state are of a different order to devising what makes good TV and brings in high ratings; that policymaking is a serious business, one that involves the weighing of evidence, the balance of competing interests and reasoned deliberation.

If Democrats choose Oprah, they would be nominating someone even better at television than Trump. But they would also be surrendering to his view that government is television. It’s not, and they need to say so. In making that argument, they will be making the case for democratic politics itself.

• Jonathan Freedland is a Guardian columnist