A century before the dawn of Instagram, Edith Wilson had her own means of distorting reality for the watchful masses. Her husband, Woodrow Wilson, was recovering from a stroke, in no shape to be seen by the public or his political foes who suspected he wasn’t up to leading a country. Unbeknown to anyone but his super-inner circle, he spent his days on his back in a hole-ridden sweater, his entire left side paralyzed.

As Rebecca Boggs Roberts details in the nail-biter opening of Untold Power: The Fascinating Rise and Complex Legacy of First Lady Edith Wilson, the woman who would stealthily become the nation’s first female acting president oversaw a meet-and-greet with a nosy band of visitors, including the secretary of state, Robert Lansing, and a couple of senators who insisted on a face-to-face. The event had all the ingredients of a disaster. Wilson’s visitors were coming under the false pretenses of discussing an international kidnapping but their true aim was to gather evidence of the Democratic president’s unfitness for office. But somehow, with the help of a circus of doctors and aides all overseen by Mrs Wilson, as well as the husband who followed her cues and even shaved for the occasion, Edith managed to leave everybody under the impression that the man supposedly running the country was in perfectly fine fettle.

As the adjectives (fascinating! complex!) of Roberts’s book’s subtitle suggest, Untold Power is not a hagiography of Edith Wilson, who grew up in Virginia and was a descendant of early English settlers and Pocahontas. Edith was not a proponent of desegregation, nor did she care about women’s right to vote, which one might think presented a complication for an author of two books on the suffragist movement. Roberts, who lives in Washington, is the daughter of the late journalist Cokie Roberts and the granddaughter of the first woman to be elected to Congress in Louisiana, Lindy Biggs. She uses Wilson’s story not as an easy sell for the Women’s History Month marketplace, but as a way to examine her city’s entrenched power systems and to shade in a chapter of US history that set in motion the feminist cause.

Edith was already widowed when she met the widower president. She was an independent woman of means, with a yen for adventure and tootling around town in her electric car. (Wilson is said to be the first woman to be given a driver’s license in DC.)

At first, Edith spurned the president’s advances. But his fixation on her wore her down, as did the joy she experienced while talking about work with a man who had the most interesting job in America. Edith concerned herself with all of her husband’s affairs, running interference and offering counsel. She was the first president’s wife to travel abroad with her husband for diplomatic trips, and also one of the first to write a memoir.

Roberts started researching for the book four years ago, while she was working as a curator at Planet Word, a Washington language museum (she’s now deputy director in the events office at the Library of Congress). She reviewed stacks of memoirs and history books, and copious letters, including the love letters that the president and his future wife sent each other when they were secretly dating.

“Edith helped define what a first lady does,” said Roberts to the Guardian. Studying Edith’s history, she came to admire a character who put her own spin on the position of first lady. “It’s an impossible job. It’s got no job description, no training, no salary, no ability to be fired. You don’t get any guardrails at all.” Roberts cites the thesis of a recent Washington Post opinion piece that sets up the binary any president’s wife faces: “The job is either undemocratic or sexist, because either the first lady is reduced to picking out china patterns or she is insisting on a political role that no one elected her to,” says Roberts.

In Edith’s case, though, such roles didn’t constitute a binary. Edith had a knack for socializing and an ability to wear down the snootiest neighbor at a dinner party, including members of European royalty who initially thought it unfit for a president’s wife to tag along on a trip to Europe to buttress support for her husband’s passion project, the League of the Nations. Her decision to accompany Woodrow raised eyebrows, and the Wilsons’ team was careful to present her role to a skeptical public as that of a tourist rather than a tinkerer. Edith was not only a shadow politician. She loved theater and opera, and was not above thinking about china and orchids. (Roberts ordered an oversized orchid pin from Etsy that she plans to wear to Edith-related speaking engagements.)

Jill Biden’s decision to continue to teach and have work outside the remit of the White House makes perfect sense to Roberts. “Maybe what she’s trying to do is find her professional fulfillment outside of the wifey role,” says Roberts. “Of course, all that means is that she’s got two full-time jobs.”

She was always at her husband’s side, an unflagging co-worker, a doting nurse, and an ingenious image crafter. “Once Woodrow Wilson got sick, she was very aware of how things looked,” says Roberts. “She was very good at sort of the public performance piece side of politics” – things like installing sheep to graze on the White House lawn as a cost-cutting measure or taking up knitting, which became the rage among American women. As her husband’s health deteriorated and she came to act as his proxy, Edith lied to Congress, the vice-president, the press and the public. “What I didn’t grasp the full extent of was that she was lying to the president too,” says Roberts. “He never knew how sick he was.”

Keeping bad news as well as public criticism from the president had a deleterious effect. When his popularity was in decline, he had no idea that it would behoove him to shore up support. The president was so unaware of his standing with the public, many of whom saw him as cold and stodgy, that he was considering running for a third term in 1920.

Edith, on the other hand, was attuned to the shifting tides. And though she was slow to jump on the progressive values that were gaining support within her party, Roberts imagines a modern-day Edith who slowly embraced new ways of thinking.

“She reminds me of my grandmother, who was also a southern woman and a very loyal Democrat, and very politically savvy and politically involved,” the author says.

“My grandmother lived to be 97, and over time she became a pretty ardent feminist.” Edith died in 1961, aged 89.

“Even if there were parts of the party that she found were moving too fast or had tactics that were too aggressive, she would have moved with the times. Because she would never, ever support the Republican party.”

• Untold Power: The Fascinating Rose and Complex Legacy of First Lady Edith Wilson is out now