Lucy Page Mercer was born on April 26, 1891, in Washington, D.C., to Carroll Mercer, a member of Theodore Roosevelt's "Rough Riders" cavalry military unit in the campaigns in Cuba, on the south shore of the island near Santiago during the brief Spanish–American War in 1898, and Minna Leigh (Minnie) Tunis, an independent woman of "Bohemian" exotic, free-spirited tastes.

[2] Though they were both from wealthy, well-connected families, Mercer's parents lost their fortune through the Financial Panic of 1893 and subsequent great recession/depression which curtailed their lavish spending.

[13] Author Persico also doubted that this was a factor, observing that Mercer's mother Minnie had divorced and remarried, and that the family had come to Roman Catholicism only recently.

[20] Winthrop Rutherfurd had proposed to socialite Consuelo Vanderbilt (1877–1964) in 1896, only to see her social-climbing mother instead force her into marriage with Charles Spencer-Churchill, 9th Duke of Marlborough (1871–1934) (cousin to later British prime minister Winston Churchill).

[30] When her husband later suffered a stroke, she contacted Roosevelt to arrange for him to be cared for at well-regarded Walter Reed Army Medical Center in Washington, D.C.[31] Historian/author Doris Kearns Goodwin speculated that an entry in the White House ushers diary for August 1, 1941 included a code name for Lucy Rutherfurd, suggesting that she attended a private dinner with the president then.

[33] In June 1944, Roosevelt requested that his daughter Anna, who was then managing some White House social functions and acting as hostess, help him arrange to meet Rutherfurd without Eleanor's knowledge.

There were supposedly several dinners in the White House's second-floor private quarters during Roosevelt's last year which were attended by Rutherfurd in a group with Anna's presence and obvious acceptance.

[35] In early April 1945, Anna arranged for Rutherfurd to come over from her South Carolina estate in Aiken to meet her father at his "Little White House" in Warm Springs, Georgia, the small plain rustic cottage built at the polio therapy center by the heated mineral water springs resort that Roosevelt helped develop beginning in the 1920s.

Rutherfurd and Shoumatoff, along with two female cousins, were sitting there while the artist worked on her painting of Roosevelt as he sat at a card table by the living room stone fireplace, fine-tuning a future speech and reading over some other papers on the early afternoon of April 12, 1945.

In this quiet domestic scene as the two had just been smiling at each other, Roosevelt suddenly placed his hand up on his forehead and temple, saying "I have a terrific headache," then slumped over losing consciousness.

Shoumatoff's presence became known and she gave a press conference to address questions, but managed to hide Rutherfurd's role, which was not mentioned in post-war biographies or administration histories for almost two decades.

[42] Roosevelt's second private secretary Grace Tully (1900–1984), who had also been at Warm Springs at the time of his death, did briefly mention Rutherfurd's presence in her 1949 memoir F.D.R., My Boss, but gave no further hint of the relationship.

[45] Historian Arthur Schlesinger Jr. (1917–2007) stated of the affair that if Rutherfurd "in any way helped Franklin Roosevelt sustain the frightful burdens of leadership in the second world war, the nation has good reason to be grateful to her.