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Protesters hold up “Not My King” signs as Britain’s King Charles III and Camilla, Queen Consort, arrive in York, England, on April 6.

LONDON — One noticeable difference between the reigns of King Charles III and Queen Elizabeth II is the splash of yellow at almost all of Charles’s public engagements. A gaggle of protesters, sometimes shouting and booing, hold aloft bright yellow signs that read “Not My King.” They are hard to miss.

The protesters’ biggest rally yet is planned for Saturday, when organizers say more than 1,000 anti-monarchists will gather along the coronation procession route in hopes of getting their message heard: King Charles, they say, should be replaced by an elected, democratic head of state.

Their view is a minority one. The majority of people in Britain support the monarchy, even if they aren’t that fussed about the coronation. They may not be draping their homes in Union Jack bunting, but they aren’t plotting a bloodless coup, either.

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A change of sovereign, though, for the first time in seven decades, has energized the republican movement and prompted others in Britain, and the 14 other countries where Charles is king, to look at the monarchy anew and begin to question aspects of its role in modern times.

Graham Smith, the head of the anti-monarchy group Republic, said Charles has been a boon for the movement.

“It being Charles and not the queen makes a big difference. She was their star player,” he told The Washington Post. “There was a lot of reluctance to criticize and challenge the queen. There was sycophancy and deference around her. That hasn’t been inherited by Charles.”

Anti-monarchist sentiment is sometimes amplified on social media, where the hashtag #NotMyKing often trends on Twitter when Charles is in the news. But the numbers of republicans spilling out onto the streets are not huge, and at events, Charles is greeted with far more cheers than boos.

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Anti-monarchy protesters gather ahead of the arrival of King Charles and Camilla at the Liverpool Central Library on April 26.

One of this week’s controversies regarding Charles had to do with the announcement of a new addition to the coronation service: an “homage of the people,” inviting Brits and other citizens of the Commonwealth to cry out their allegiance in unison. A tweet from the Republic account calling it “an offensive and tone deaf gesture that holds the people in contempt” received nearly 10,000 likes and more than 3,000 retweets.

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Republican activists are hoping to capitalize on those moments of pushback, as well as longer-term softening of support for the monarchy. A recent survey by the National Centre for Social Research found that a record-low 29 percent of people said the monarchy is “very important.”

A deeper dive into the figures suggests that the monarchy could have a succession problem, with younger people in particular turning their backs on it. Only 12 percent of those ages 18 to 34 view the monarchy as “very important.”

And Charles, while liked well enough by a majority of Brits, is not nearly as popular as his mother was.

Jacob Goodman, a 26-year-old Londoner who was at a recent #NotMyKing event, said that “everyone liked the queen” but that many people saw her as separate from the institution she represented. “It would be very odd to me to know a young person who is pro-royal. I’d probably think they are lying,” he said.

Others at the London protest said that they didn’t want to jettison the monarchy but that the change from “God Save the Queen” to “God Save the King” had gotten them thinking.

“I understand the need for a monarchy,” said Andrew Lowe, 52, an architect. “I question the size of it and the cost of it and the heritage behind it. With the change from the queen to the king, it’s a chance to debate the subject.”

To be sure, Elizabeth was not universally loved. A British teenager fired blanks at her while she was on horseback in the 1981 Trooping the Colour ceremony. She was hit with eggs during a 1986 trip to New Zealand, the yellow yolk running down her pink dress. A protester shouted at her “You should be ashamed!” during a 2007 Westminster Abbey service commemorating the 200th anniversary of the abolition of the slave trade. When she visited Dublin in 2012, she was met with signs reading “Britain out of Ireland.”

In the course of her reign, 17 countries delivered the ultimate protest by removing her as their queen.

But during her everyday engagements in Britain, Elizabeth was rarely confronted with anti-monarchy demonstrations.

Since Charles became king, protests have become the norm at royal events. He was heckled at a Commonwealth Day event at Westminster Abbey; booed when visiting a zoo in Colchester; and targeted with eggs in York as a demonstrator shouted: “This country was built on the blood of slaves.”

Last month, a couple from a youth movement called No More Royals jumped over the security rope at Windsor Castle and lay down on a bed made for King Charles II and read a copy of Prince Harry’s scathing memoir, “Spare.”

Symon Hill, a tutor and activist from Oxford, was arrested in September after he shouted “Who elected him?!” as a document formally proclaiming Charles as king was read aloud.

Hill said that for many with republican leanings, Elizabeth was “always just there, like rivers and mountains,” but now people are “more bothered because it feels like they are actively being told to accept something.”

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Protesters hold “Not My King” fliers ahead of the arrival of Charles and Camilla in Liverpool.

Britain in 2023 is a very different country than it was in 1953, the year of the last coronation. At the time, Elizabeth was just 27 and Britain was coming out of World War II. On the eve of the coronation, a British-led expedition climbed Everest.

“You had this very young queen, this titan of world affairs with Winston Churchill in Downing Street, and she was a sort of fairy-tale princess, a symbol of rejuvenation. And we’re just not in that place now,” said Robert Hardman, author of “Queen of our Times.”

Charles, at 74, will be the oldest monarch ever crowned at Westminster Abbey, and the ceremony is coming at an uncertain moment as Britain tries to establish its post-Brexit place in the world — while facing double-digit inflation.

Norman Baker, author of a book on royal finances, said he believed that most Brits want a royal family, “but one which is a bit more normal, a bit more accountable, a lot less expensive.”

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The British monarch doesn’t have political power but is still involved in the business of government. Constitutional obligations include formally appointing ministers, opening Parliament, signing state papers, and meeting with the prime minister once a week for an “audience” where the monarch can “advise and warn.” Some prime ministers over the years reported enjoying those sessions with Elizabeth. But it still means that the very busy leader of the country needs to reserve time to go to Buckingham Palace on Wednesday evenings.

Anti-monarchists argue that Britain should have an elected head of state who can actually intervene in politics and provide a check on the government.

For instance, when then-Prime Minister Boris Johnson advised the queen to dissolve Parliament at the height of the Brexit crisis — unlawfully, it turned out — it was unthinkable she would do anything but act on the advice of her government. But an elected head of state presumably could have declined Johnson’s request without sparking a constitutional crisis.

The republicans will still have a tough time getting traction for their ideas. The elected leaders of both Scotland and Wales are anti-monarchists. But there is no political appetite from the two main political parties to change the duties of the king. And only about a quarter of Brits tell pollsters that the monarchy is “not at all important” or is worthy of abolishing.

A bigger threat to the monarchy may come from the royal family itself, said Craig Prescott, an academic at Bangor University and author of an upcoming book on the modern monarchy. He said the royals “endure very intense press intrusion” and aren’t able to “express their own views or choose a career.”

“It’s understandable that Prince Harry chose to leave and pursue a private life. What happens if Prince George thinks that Uncle Harry was right and it’s not worth living in a goldfish bowl? What then?”