State dinner connoisseur Roxanne Roberts shares some little-known facts about the grand affair. (Jhaan Elker, JulieAnn McKellogg and Jason Aldag/The Washington Post)

When France’s recently dumped first lady was asked last year which political spouse had made the biggest impression on her, she said one was particularly warm and friendly.

“Michelle Obama told me it took her a year to settle into the role; she also made some faux pas at the start,” Valérie Trierweiler said to Britain’s Sunday Times five months ago. “That’s pretty much the case for all of them, and they all suffered attacks.”

Tuesday night, there will be no swapping of stories between first ladies as the White House hosts the French delegation for a state dinner. Trierweiler and Michelle Obama won’t have a chance to catch up, because French President François Hollande curtly broke up with his longtime girlfriend two weeks ago. The separation came after he was caught by paparazzi leaving an actress’s borrowed apartment on the back of a moped.

Le scandale, which occurred after the Obamas had issued a formal invitation to both Hollande and Trierweiler, was but a wrinkle for the White House protocol machine. The Élysée Palace removed Trierweiler’s page from its official Web site, and the White House similarly struck her from the state dinner guest list when Hollande announced in an 18-word dictum that his longtime partner, a journalist with whom the French president had been associated since his 2007 split, would no longer serve as first lady.

The party must go on, right?

“The White House is flexible that way. We can invite her, and you can tell us she’s not going to be coming, and we don’t ask why,” says Pamela Eyring, president of the Protocol School of Washington, which for 25 years has trained high-level U.S. government protocol officers.

Hollande’s complicated personal life is not that rare where French leaders are concerned.

In November 2007, Nicolas Sarkozy arrived at the North Portico looking chipper and even a tad relieved. It was just three weeks after his divorce from second wife Cécilia Ciganer-Albéniz, who left him for another man and then reconciled shortly before Sarkozy was elected. The two quickly called it quits, however, and the new bachelor was in an expansive mood when he exchanged toasts with President George W. Bush — probably because half of the women in France were throwing themselves at him, his ex-wife later sniffed. Just a few days after returning home, Sarkozy met former model/singer Carla Bruni, who became France’s first lady three months after a whirlwind romance — but she never appeared, alas, at a formal White House dinner.

While protocol traditionally discouraged putting a nontraditional romantic relationship on display at a state dinner, wives are not mandatory dinner guests.

When China’s President Hu Jintao was honored by the Obamas in 2011, his wife, Liu Yongqing, stayed home — with no eyebrows raised in the media. Another bachelor — the divorced Japanese Prime Minister Junichiro Koizumi — got a state dinner in 2006 and (a dream come true for an Elvis fan) a trip to Graceland with President George W. Bush.

Many guests of honor opt to bring their daughters, a practice going back for more than 50 years. In July 1961, the Kennedys welcomed Pakistani President Mohammad Ayub Khan and his daughter, Begum Nasir Akhtar Aurangzeb, to the famous state dinner held at Mount Vernon — the only such event ever held outside of Washington. Four months later, they hosted Indian Prime Minister Jawaharlal Nehru and his daughter (and future prime minister) Indira Gandhi. In 1991, King Hassan II of Morocco was invited to the White House by President George H.W. Bush, and brought along his daughter, Princess Lalla Meryem.

But the most famous father-daughter star turn was at the state dinner for Nelson Mandela in October 1994. South Africa’s new president, who was given a hero’s welcome by official and unofficial Washington, was separated from wife Winnie and accompanied by his youngest daughter, Zindzi. “Mr. President, I know how proud you are to have your daughter Zindzi with you on this trip, and I am proud to have her as my dinner partner tonight,” President Bill Clinton said in his toast.

Aside from personal bonding and serving as cultural ambassadors, the truth is that spouses on these visits have very light agendas. While the leaders hold bilateral meetings during the day of the dinner, their spouses typically take in a cause near and dear to one or both. (Joachim Sauer, the very private husband of German Chancellor Angela Merkel, was spared a first spouse field trip in 2011.) “You can do as little as you want — a coffee and conversation — or take them to a visit in Washington or beyond,” says Anita McBride, former chief of staff to Laura Bush.

But once in a great while, it’s probably better if the head of state comes alone. When all goes well, the spouses pose for some pretty pictures and give the media something to do before the dinner itself. But when the relationship between the first ladies hits Def Con 2, things can get ugly. Exhibit A: Raisa Gorbachev and Nancy Reagan.

The two strong-willed first ladies – despite repeated assurances of mutual admiration and respect — engaged in their own Cold War of dislike and one-upmanship for years. Before the 1987 state visit to Washington, the Russian first lady waited two weeks to accept an invitation for tea with her American counterpart, then switched it to morning coffee so she could meet with American publishers and editors instead — a snub that didn’t go over well in the East Wing.

“I don’t know, perhaps glasnost and graciousness don’t go on the same G page in the Russian dictionary,’’ a White House official snarked to the New York Times. When Nancy Reagan went through with a planned tour of the White House (“This is where we were last night,” she said entering the State Dining Room), Gorbachev was unimpressed: “It seems to be smaller today.”

Michelle Obama’s role has been shifted only slightly by Hollande’s decision to come stag, says Eyring, the protocol expert. Obama had hosted Trierweiler along with other G-8 spouses last spring for a ladies tour of the White House and a luncheon that included vegetables from the South Lawn’s garden. This go-round, the first lady will not host a spouses’ event for the cameras, but still she had plenty to do to prepare.

“With her social secretary, she helps to build that guest list. There’s the seating, and it’s critical to have the right celebrity at the right table,” Eyring says. “She has to be very involved because this dinner represents her husband and herself. You want everyone to walk away with warm feelings.”

Such first lady fustiness may be too passé for the French, who aren’t pining for Hollande to find a new first lady. Trierweiler’s favorability ratings were never very high, and the role is viewed as having little official significance.

“It’s not like an institution is not being fulfilled at the moment,” says Andrew Sobanet, chair of the French Department at Georgetown University. “One does not need to see photos of the president with his family or the Élysée Palace dog.”

Nor, as Trierweiler has learned, does international diplomacy require la première dame dressed in a flowing gown at a state dinner.