When a brash former president weighs in on the comportment of an outspoken former American actress turned princess, the results were never going to be a publicity agent’s dream. They do, though, confirm a certain reality: Meghan Markle is a lightning rod from London to Los Angeles.

What President Trump had to say about the duchess of Sussex fell in line with a new poll of the British public indicating that Meghan and Harry are, with the exception of the disgraced duke of York, Prince Andrew, the least popular British royals.

The poll, spearheaded by a former U.K. Conservative deputy chairman, Lord Ashcroft, suggests that the approval rating of the duke of Sussex is a dismal 22 percent, and that of his wife is even lower, at a dreary 18 percent. Prince Andrew, after settling a lawsuit from a woman who accused him of sexually assaulting her when she was in the clutches of his dear friend, Jeffrey Epstein, has seen his popularity dip into single-digit territory. 

During the course of a visit to Scotland this week Mr. Trump told a British politician, Brexit advocate, and broadcaster, Nigel Farage: “I think she [Meghan] has been very disrespectful to the queen. How can you be so disrespectful to the queen?” 

Mr. Trump, who’s made this criticism of the duchess before, spoke glowingly of the late Queen Elizabeth II, and with respect to the upcoming coronation of her son, King Charles III, said, “I got to know him [Charles] quite well and he loves the country, really loves the country and he loved his mother.” He continued, “And that’s why I thought she was treated so disrespectfully by Meghan — and just no reason to do that. I was actually surprised that Harry was invited, to be honest.”

To that point, there is growing speculation among “royal watchers” in the U.K. that in the end, Harry isn’t going to go to the coronation at all — that he’ll find a last-minute excuse to stay in Montecito rather than stand shamefully in a back row at Westminster Abbey, not allowed to wear his military uniform as he is no longer “a working royal.” Meghan, of course, would be driving the decision, or so the speculation goes.

The royal watchers are also wondering if Meghan will find a way to distract attention from the big event in London. The Sussexes have a way of doing that, such as giving their big interview with Oprah Winfrey while the prince consort, Philip, was in ailing health. Some observers even blamed them, perhaps unfairly, for his passing soon thereafter.

A former Fox News anchor, Megyn Kelly, told the British cable channel GB News (for which Mr. Farage is currently a presenter) that “very clearly in the U.K., the people cannot stand them, especially her.” She added, “Even here in the United States, everybody said we don’t want anything to do with them.”

Ms. Kelly cited a recent Newsweek poll that according to her showed that “only 33 percent of Americans like her and only 39 percent like him.” 

In her view the press whirlwind around the couple’s Netflix documentary “Harry & Meghan” combined with the release of Harry’s memoir “Spare” accelerated the royal couple’s plummeting popularity ratings. “They went off a cliff,” Ms. Kelly said.

While Prince Harry has an ax to grind with his famous family — despite leading a life of comfort and privilege unimaginable for most people — for the duchess of Sussex things simply do not add up. The “disrespectful” behavior, as Mr. Trump put it, that she has displayed toward the institution of the monarchy, if not Queen Elizabeth herself, has come in different forms. One of the most public ways she did was to mock the traditional curtsy that ladies were expected to do when greeting the queen. 

Something else she will not be doing: attending the coronation of King Charles at Westminster Abbey on May 6. Neither will President Biden, which for Mr. Trump is another example of “disrespectful,” but to be fair, he also said of the 80-year-old Mr. Biden: “I don’t think he can do it physically, actually. I think that it’s hard for him to do it physically, I think, getting over here for him. He’s got a lot of things going on, and a lot of strange things happen.”

What then, is Ms. Markle’s excuse? The one tossed out to the press — that the duchess needs to stay home in California for the 4th birthday of her son, Prince Archie — seems less than robust considering that her newfound level of wealth flying to London and back in the same 24-period is easily within the realm of possibility. 

That is, after all, what Prince Harry intends to do. According to British press reports, the adoptive Californian will be on a plane heading back to America within just two hours of the conclusion of the coronation ceremony. 

While Mr. Trump was correct in identifying Ms. Markle’s problematic relationship with the royal family, and while the press hoopla over the the couple’s documentary and Prince Harry’s artfully ghostwritten memoir was widely perceived as both overkill and crass, there could be something else to the dwindling popularity of the Sussexes, and of Meghan in particular. 

Americans don’t do royalty, but we do take a shine to royal traditions. The 1981 royal wedding of Charles and Diana on July 29, 1981, was watched by more than 750 million people, and American television viewers were riveted by the glamor of nuptials that sadly were not to last. 

There is a sense that despite the almost unbelievable opportunities afforded her by marrying the king’s youngest son, Ms. Markle has more or less squandered them all on the altar of Hollywood. If Hollywood was not exactly kind to the former “Suits” star — only fools think that industry is nice to anyone — would Britain and the world have been any kinder? Her own narcissism intruded before she could really give either a chance.