Question: The book "The Gay Place" contains characters based on the first lady who was the wife of the President of the United States who was which number in the succession?

Context articles: Lady Bird Johnson
The Gay Place
Vicki Risch
List of current United States first spouses
List of First Ladies of the United States
Edith Roosevelt
Anna Harrison
First Lady of the United States
First Lady of Austria
Office of the First Lady of the United States

Claudia Alta "Lady Bird" Johnson (née Taylor; December 22, 1912 – July 11, 2007) was First Lady of the United States (1963–69), as the wife of the 36th President of the United States, Lyndon B. Johnson.
The Gay Place (1961) is a series of three novellas, with interlocking plots and characters, by American author Billy Lee Brammer.
 The novellas, published in a single book, include "The Flea Circus", "Room Enough to Caper" and "Country Pleasures".
 Set in an unnamed state identical to Texas, each novella has a different protagonist: Roy Sherwood, a member of the state legislature; Neil Christiansen, the state's junior senator; and Jay McGown, the governor's speechwriter.
 The governor himself, Arthur Fenstemaker, a master politician (said to have been based on Brammer's mentor Lyndon Johnson) serves as the dominant figure throughout.
 The book also includes characters based on Brammer, his wife Nadine, Johnson's wife Ladybird, and his brother Sam Houston Johnson.
Vicki Risch is the former First Lady of Idaho and the wife of U.S. Sen. Jim Risch, who served as Governor of Idaho in 2006.
 She became First Lady on May 26, 2006, when her husband succeeded former Gov. Dirk Kempthorne, who resigned to become United States Secretary of the Interior.
 Mrs. Risch succeeded former First Lady Patricia Kempthorne who had held the post for over seven years.
 Mrs. Risch served as First Lady until January 2007, as her husband did not seek a full term as governor, but rather was reelected to his old post as lieutenant governor.
In the United States, the first spouse (first lady for women, first gentleman for men) is the term used to refer to the spouse of a chief executive - that is, of the spouse of the President of the United States (the First Lady of the United States and the First Gentleman of the United States) and the spouses of the governors of the 50 U.S. states and U.S. territories (Guam, Northern Mariana Islands, Puerto Rico, American Samoa, and the United States Virgin Islands) and the spouse of the mayor of the District of Columbia.
 (The spouses of many mayors are often called the "first lady" or "first gentleman" of the city as well, and the use of the terms sometimes extends even to the spouses of college presidents).
The First Lady of the United States is the hostess of the White House.
 The position is traditionally filled by the wife of the President of the United States, but, on occasion, the title has been applied to women who were not presidents’ wives, such as when the president was a bachelor or widower, or when the wife of the president was unable to fulfill the duties of the First Lady herself.
 The First Lady is not an elected position; it carries no official duties and receives no salary.
 Nonetheless, she attends many official ceremonies and functions of state either along with or in place of the president.
 Traditionally, the First Lady does not hold outside employment while occupying the office.
 She has her own staff, including the White House Social Secretary, the Chief of Staff, the Press Secretary, the Chief Floral Designer, and the Executive Chef.
 The Office of the First Lady is also in charge of all social and ceremonial events of the White House, and is a branch of the Executive Office of the President.
Edith Kermit Carow Roosevelt (August 6, 1861 – September 30, 1948) was the second wife of President Theodore Roosevelt and served as First Lady of the United States during his presidency from 1901 to 1909.
 She was the first First Lady to employ a full-time, salaried social secretary.
 Her tenure resulted in the creation of an official staff, and her formal dinners and ceremonial processions served to elevate the position of First Lady.
Anna Tuthill Symmes Harrison (July 25, 1775 – February 25, 1864), wife of President William Henry Harrison and grandmother of President Benjamin Harrison, was nominally First Lady of the United States during her husband's one-month term in 1841, but she never entered the White House.
 At the age of 65 years during her husband's presidential term, she is the oldest woman ever to become First Lady, as well as having the distinction of holding the title for the shortest length of time, and the first person to be widowed while holding the title.
 She was the last First Lady to have been born in British America.
First Lady of the United States (FLOTUS) is the informal but accepted title held by the wife of the President of the United States, concurrent with the president's term of office.
 Although the first lady’s role has never been codified or officially defined, she figures prominently in the political and social life of the nation.
 Melania Trump is the current First Lady.
The First Lady of Austria is the title attributed to the wife (or, in place of a wife, a designee, such as a daughter) of the President of Austria.
 The current First Lady is Doris Schmidauer, wife of President Alexander Van der Bellen, who has held the position since 26 January 2017.
The Office of the First Lady of the United States is the staff accountable to the First Lady of the United States.
 The office and its responsibilities, while not mandated, have grown as the role of the First Lady has grown and formalized through the history of the United States.
 The Office of the First Lady is an entity of the White House Office, part of the Executive Office of the President.