I am not immune to Oprah’s charms, but President Winfrey is a terrible idea. It also underscores the extent to which Trumpism — the kowtowing to celebrity and ratings, the repudiation of experience and expertise — has infected our civic life. The ideal post-Trump politician will, at the very least, be a deeply serious figure with a strong record of public service behind her. It would be a devastating, self-inflicted wound for the Democrats to settle for even benevolent mimicry of Mr. Trump’s hallucinatory circus act.

Indeed, the magical thinking fueling the idea of Oprah in 2020 is a worrisome sign about the state of the Democratic Party. That Ms. Winfrey could probably beat those considered likely front-runners — Joe Biden, Bernie Sanders, Kirsten Gillibrand — is testament to how demoralized and devoid of fresh political talent the post-Obama party has become.

In a way, the conversation on the left (and the anti-Trump right) around Ms. Winfrey is more troubling than the emotional immaturity and anti-intellectualism pulsing out of the red states that elected Mr. Trump. Those voters have long defined themselves in opposition to the intellectual seriousness Democrats purport to personify.

If liberals no longer pride themselves on being the adults in the room, the bulwark against the whims of the mob, our national descent into chaos will be complete. The Oprah bandwagon betrays the extent to which social causes and identities — and the tribal feelings they inspire — have come to eclipse anything resembling philosophical worldviews. American politics has become just another team sport, and if suiting up a heavy hitter like Ms. Winfrey is what it takes to get the championship ring, so be it.

The idea that the presidency should become just another prize for celebrities — even the ones with whose politics we imagine we agree — is dangerous in the extreme. If the first year of the Trump administration has made anything clear, it’s that experience, knowledge, education and political wisdom matter tremendously. Governing is something else entirely from campaigning. And perhaps, most important, celebrities do not make excellent heads of state. The presidency is not a reality show, or for that matter, a talk show.

To her credit, last year Ms. Winfrey told CBS, “There will be no running for office of any kind for me.” But when the conservative columnist and Trump critic John Podhoretz published an essay in The New York Post in September headlined “Democrats’ Best Hope for 2020: Oprah,” she retweeted it.

“If any figure in the United States bears watching over the next couple of years as our political culture continues the radical transformation that led to the election of Donald Trump, it’s Oprah,” Mr. Podhoretz wrote. “I believe she’s uniquely positioned, should she wish to commit herself, to seek the Democratic nomination for president and challenge Trump in 2020.”

Let us hope, for the sake of our nation, that she does not want it.