A Spy Cam. A Dior Pouch. And South Korea’s First Lady.

The president was grappling with a slowing economy, a deadly crowd crush and nuclear threats from a belligerent neighbor. Then came a much more personal scandal: spy cam footage that showed his wife accepting a $2,200 Dior pouch as a gift.

It has quickly escalated into one of the biggest political crises for President Yoon Suk Yeol of South Korea, who has made his mark in foreign policy by aligning his country more closely with the United States and Japan but has been bogged down by controversies at home, many of them involving the first lady, Kim Keon Hee.

The video of Ms. Kim, which emerged late last year, has caused a rift between Mr. Yoon and one of his most trusted lieutenants. It has roiled his political party — one senior member called on Ms. Kim to apologize and compared her to Marie Antoinette. And, polls show, it has become a significant issue ahead of crucial parliamentary elections in an increasingly polarized political atmosphere.

For nearly two years, Ms. Kim has challenged how this deeply patriarchal society views the role of the presidential spouse. Unlike ​past first ladies, who typically remained in the shadow of their husband, she has reveled in media attention and even publicly pushed Mr. Yoon’s government to ban the breeding and butchering of dogs for human consumption. She has talked about Mr. Yoon’s devotion to her, saying in 2022 that he had vowed to cook for her and “kept that promise for the past decade.”

But Ms. Kim has also frequently courted controversy, sometimes in ways that, critics say, highlight her undue influence on the government.

In 2021, when Mr. Yoon, a former prosecutor, was campaigning for the presidency, she apologized for inflating her résumé to promote her art-exhibition business. Then came the release of conversations with a reporter, who secretly recorded Ms. Kim suggesting that she was deeply involved in her husband’s campaign​. She called Mr. Yoon “a fool” who “can’t do anything without me.”​ She also declared that she would retaliate against unfriendly media “if I take power.”

Ms. Kim has also faced allegations that she was involved in a stock price manipulation scheme before Mr. Yoon’s election. In December, the opposition-controlled Parliament passed a bill that would have mandated a special prosecutor to investigate the claims. Mr. Yoon, 63, who like Ms. Kim, 51, has denied the accusations, vetoed the bill.

Mr. Yoon, who has said his “happiest memory” was of marrying Ms. Kim in 2012, has not been able to move on from the Dior footage.

The video was taken in September 2022 by a Korean American pastor named Choi Jae-young with a camera hidden inside a wristwatch. The first news report of the episode came more than a year later, from a left-leaning YouTube channel called the Voice of Seoul, the same outlet that released Ms. Kim’s chat with a reporter.

The footage shows Mr. Choi visiting Ms. Kim in her personal office outside the presidential compound and presenting her with the gift.

“Why do you keep bringing these?” Ms. Kim is heard saying. “Please, you don’t need to do this.”

Mr. Choi advocates friendly relations between North and South Korea, while Mr. Yoon has taken a more aggressive stance toward the North. He said he got to know Ms. Kim when Mr. Yoon was running for president and received an invitation to Mr. Yoon’s inauguration in May 2022. He visited Ms. Kim’s office a month later to thank her and said he gave her a $1,300 Chanel cosmetics gift set.

During that meeting, Mr. Choi said that he overheard a conversation in which Ms. Kim appeared to be playing a role in the appointment of a senior government official. He said that is when he decided to “expose” her. A Voice of Seoul reporter provided him with the spy cam and the cloud blue calfskin Dior pouch, and Mr. Choi sent a photo of the Dior bag to Ms. Kim, asking for another meeting.

Mr. Choi said that although he had asked to meet the first lady several times, he was granted an audience only twice and only when he let her know in advance that he was bringing expensive gifts. Government officials and their spouses are banned from accepting a gift worth more than $750 even if no potential conflict of interest is involved.

“The gift was a ticket to an audience with her,” Mr. Choi said.

In the video, Ms. Kim also expressed her desire to “involve myself actively in South-North Korean relations,” raising fears that she was overstepping her role.

As the scandal has raged, Ms. Kim has avoided public appearances for one and a half months. Mr. Yoon’s office said the president and Ms. Kim had “nothing to share” on the matter.

Ms. Kim has not publicly commented on the various allegations against her since her 2021 apology, when she said she would “stick to ​a wife’s role” if Mr. Yoon was elected. But ​during a rare interview, with Artnet News​ last year, she signaled a shift, saying that she wanted to become “a K-culture salesperson​” and support​ Mr. Yoon and his government in “cultural diplomacy.​”

In the conversations recorded by Mr. Choi and Voice of Seoul, she appeared to deny claims of wrongdoing, characterizing them as political smear campaigns​.

Some officials from Mr. Yoon’s People Power Party have accused Mr. Choi of setting a “trap” for Ms. Kim and timing the release of the video to influence the April election. They have also said that Ms. Kim has not used the bag, which has been stored in a presidential repository.

A majority of South Koreans, in surveys, say it was inappropriate for Ms. Kim to accept the pouch and say they want an investigation and an explanation from Mr. Yoon.

​ “This is an explosive issue” because it reminds South Koreans of the recurring corruption that has disgraced most of the country’s former presidents, said Ahn Byong-jin, a political scientist at Kyung Hee University in Seoul​.

Some members of Mr. Yoon’s party have demanded an apology from Ms. Kim as damage control. The opposition accused Ms. Kim of influence-peddling and “manipulating government affairs.” Mr. Yoon, they added, was being excessively protective of his wife, in stark contrast to his government’s aggressive pursuit of corruption charges against Lee Jae-myung, the opposition leader.

Mr. Yoon was also faulted by his allies in the media.

“The conservatives of this country can no longer carry the ‘Kim Keon Hee risk,’” said a columnist in the conservative daily Dong-A Ilbo.

With pressure mounting, the chairman of the P.P.P., Kim Gi-hyeon, stepped down. Mr. Yoon replaced him with a close ally, Han Dong-hoon. But Mr. Han has appeared to criticize the administration’s handling of the scandal and appointed the senior official who went on to compare Ms. Kim to Marie Antoinette, a criticism that resonated widely among the public.

Mr. Yoon then demanded Mr. Han’s resignation, according to local media, but by last week the two men appeared to have stuck an uneasy truce.

Their handling of the scandal has shown how much influence Ms. Kim wields within Mr. Yoon’s office, political analysts said. This is why South Koreans joke, Mr. Ahn said, that “there are two V.I.P.s in Yoon’s office and V.I.P. No. 1 is Kim Keon Hee.”