Kate Andersen Brower is the author of the best-sellers "First Women: The Grace and Power of America's Modern First Ladies" and "The Residence: Inside the Private World of the White House." Unless otherwise noted, facts in this piece reflect research from those works. The opinions expressed here are hers.

(CNN) Every four to eight years, the peaceful transition of power occurs that is so crucial to our democracy. But this time, because the campaign was so full of vitriol, it is even more consequential. And it is first lady Michelle Obama who must serve as the welcome committee.

Less than 48 hours after Donald Trump's surprise victory, Michelle Obama sat down for tea in the Yellow Oval Room with the president-elect's wife Melania. "We are going to be there for the next president and do whatever we have to do to make sure that he is successful, because if he succeeds we all succeed," the outgoing first lady said in her interview with Oprah Winfrey that aired Monday night on CBS.

Her door, she said, is always open to Melania and her East Wing staff.

Now we know that in addition to discussing with Melania the challenges that come with raising young children in the White House, the first lady extended a peace offering, one that had been extended to her eight years earlier by Laura Bush.

The first lady's honesty was remarkable to me because she openly expressed what so many of the women before her have felt: allegiance to the American presidency and dedication to the peaceful transfer of power mixed with very real human emotion.

Instead of leaving a letter behind, as presidents traditionally do for their successors, outgoing first ladies give a tour of the residence to the women who follow them. During that tour, they position the incoming first lady at a specific spot in the first lady's dressing room. Here, Hillary Clinton told Laura Bush: "Your mother-in-law stood right here and told me that from this window you can see straight down into the Rose Garden and also over to the Oval Office." Eight years later, when Michelle Obama came for her first tour of the White House, Laura showed her the exact same spot.

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The transition from the Bushes to the Obamas has been among the most pleasant in modern history. When I interviewed her for my book "First Women," Laura Bush's chief of staff, Anita McBride, described her meeting with Michelle Obama's staff, including her then-chief of staff Jackie Norris, and the day they spent together in the East Wing in late December 2008 before the Obamas moved in.

They broke up into groups and exchanged detailed information, down to lists of specific events typically attended by the first lady, including those that could be safely skipped and those commitments that had to be honored. Michelle Obama surprised Laura Bush when, on the morning of the inauguration, she presented her with a leather journal and engraved silver pen knowing that she was working on her memoir. Since then, Laura Bush and Michelle Obama have forged a friendship working on humanitarian initiatives together, even as President Obama campaigned in part against President Bush's policies.

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Not so for other first ladies. One of the most difficult transitions came in 1960, when Republican President Dwight D. Eisenhower, who had been supreme commander of the Allied fForces in Europe during World War II, was replaced by the young, privileged Democrat John F. Kennedy, whom he called "the boy."

Mamie Eisenhower, 64, resented Jackie Kennedy, who was only 31 years old at the time, and she caustically referred to her as "the college girl."

During her White House tour, Jackie was recovering from a cesarean section for the birth of John Kennedy Jr. and she had been told that a wheelchair would be made available. After more than an hour and a walk-through of some thirty rooms with Mamie Eisenhower, Jackie emerged from the White House looking pale and worn out. Later, Jackie would say she was "too scared" of Mamie to ask where her wheelchair was.

On the cold January day in 1969 when Richard Nixon was sworn in, LBJ's wife, Lady Bird, made small talk with Pat Nixon during the awkward ride the outgoing and incoming first lady take together to the Capitol swearing-in ceremony.

As it has been on every Inauguration Day in modern history, a car packed with Secret Service agents separated them from the car their husbands shared. "I'm so happy it didn't sleet today," Lady Bird said. "We might get lucky and have no rain," Pat replied as they drove down Pennsylvania Avenue. The ride was familiar: Lady Bird and Pat had made the same trip eight years earlier as second ladies, when Pat was leaving Washington and Lady Bird was taking her place.

Twelve years later, when they rode in a limo from the White House to the Capitol on Inauguration Day, Rosalynn Carter "just looked out the window," Nancy Reagan wrote in her memoir, My Turn. "She didn't say a word."

Rosalynn Carter told me she still remembers those agonizing weeks after her husband lost and before they moved out: "You lose the election on November 4, and then you're just ready to go home." For Rosalynn, it was especially difficult as she watched her husband work to free American hostages held in Iran only to have them released minutes after President Reagan was sworn in.

When Nancy Reagan came for her tour of the residence, Rosalynn walked her through the second and third floors and talked about her work to showcase American art. But the tour was short and she never showed Nancy the presidential bedroom and study.

Their relationship was not helped by rumors that Nancy wanted the Carters to move out a few weeks before the inauguration and live in Blair House, across the street from the White House, so that she could begin redecorating.

One would think the transition from the Reagans to the Bushes would have been smoother, since Barbara Bush had been the second lady for eight years. But Nancy Reagan and Barbara Bush were not close and Barbara had never been in the residence.

In an interview, Barbara Bush told me that the chief usher came to the vice president's residence to show her pictures of the rooms on the second and third floors of the White House. "I really didn't know anything about the upstairs at the White House to speak of."

After her husband was elected, Barbara's chief of staff, Susan Porter Rose, said, "Although I immediately gave Mrs. Bush the floor plan of the White House so she could be thinking about their new living arrangements ... She would have loved to have actually seen the place, what the closets were like, et cetera, but that unfortunately was not to be."

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No transition has been entirely smooth, whether because the president is being replaced by someone from an opposing political party or because personal relationships have been frayed among politicians within the same party.

But, just as there is among presidents, there is empathy and understanding among the women who have served as first lady. As Lady Bird Johnson boarded the plane that would take her and her husband home to Texas, she was touched when she found a large bunch of yellow roses from the Nixons at her seat. Pat knew they were her favorite flower.