Barbara A. Perry, Gerald L. Baliles Professor and Presidential Studies Director at the University of Virginia’s Miller Center, is the author of “Jacqueline Kennedy: First Lady of the New Frontier” and “Rose Kennedy: The Life and Times of a Political Matriarch.”

My one and only meeting with first lady Barbara Bush came just six months before she died. The occasion was the 20th anniversary celebration of her husband’s presidential library at Texas A&M University. As I sat in the green room, preparing to go on stage for a panel on President George H.W. Bush, his wife suddenly appeared at the door in her electric scooter. I approached to introduce myself, thinking that our shared first name might offer an instant connection. When none was forthcoming, I offered, “At UVA’s Miller Center I worked on your husband’s oral history.” Still no response. Before flop sweat overtook me, I retreated to my standard but heartfelt line, reserved for all who have made it to the White House: “Thank you for your service to our country.” The first lady trained her steely blue-gray eyes on me and snapped, “Baloney!”

In my brief encounter with her, I was exposed to the full Barbara Bush treatment. This well-known side of the first lady’s vinegary personality appears frequently in Susan Page’s new biography, “The Matriarch.” But Page, the Washington bureau chief of USA Today, has written a more complete and highly readable portrait of the wife of the 41st president and mother of the 43rd. Only the second first lady to hold that distinction, as a wife and mother of presidents (Abigail Adams was the other), Bush must rank among the premier political matriarchs in American history, along with Rose Kennedy. Unlike the Kennedys, however, the Bushes eschew the dynastic label, believing that it makes them seem entitled.

And yet entitled they were. George H.W. Bush was born into privilege, and his future wife lived a comfortable upper-middle-class childhood in Rye, N.Y. What makes Page’s biography such a notable contribution to our understanding of Barbara Bush is the access she gave the author to private diaries dating to 1948 and five interviews she granted in the months before her death. The narrative also benefits considerably from conversations Page conducted with Bush 41 and 43; President Bill Clinton; and more than 100 Bush family members, friends and former aides.

We learn that Barbara Pierce, born in 1925, adored her father, Marvin, a successful businessman who would become publisher of McCall’s magazine, but she had a fraught relationship with her mother, Pauline, that contributed to Barbara’s harder edges. Caught in the pre-World War II expectations that young society girls attended prep school and “finished” at women’s colleges, Barbara had no plans to pursue a career outside the home. Swept off her feet at age 16 by a dashing Andover student, “Poppy” Bush, at a 1941 Christmas dance, she dropped out of Smith after her freshman year to await the return of her beau from the South Pacific, where he had become a decorated war hero for surviving Japanese fire that crashed his fighter plane.

Page begins her book with a chapter on the crucible that shaped the marriage of George and Barbara Bush, the well-known tragedy of their daughter Robin’s death from leukemia at age 3 in 1953. Before that trauma, the couple seemed to have it all as they started a new life in the rough-and-tumble Texas oil country, far from the ease of Northeastern high society. But then they lost their young daughter. They would never stop missing Robin or pining for her presence. A most revealing passage about Bush’s policy positions as a political wife reveals how holding her dying daughter and feeling the little girl’s soul dissipate shaped her posture toward abortion. In a 1980 diary entry, she explained that life begins at birth, when the soul enters the body. She concluded that “abortion is personal, between mother fathers and Dr.” and “not [underlined twice] a Presidential issue.”

Much as it did for the Kennedys, tragedy haunted the Bushes. After Robin’s death, Barbara lost her mother in a car accident and suffered a miscarriage while her husband was away on business in the early 1960s. As his career in oil and then politics soared, she was left to govern an eventual brood of four rambunctious sons and one adored daughter. Approaching mid-life, she fell into a deep depression and even contemplated suicide.

Also like the Kennedy women, Bush had to endure the humiliation of rumors that her husband maintained a romantic relationship with a younger woman. The trust that Page developed with Bar, as the Bushes nicknamed her (after a horse at the family compound in Kennebunkport!), did not stop the author from addressing inconvenient truths.

Bush was no Eleanor Roosevelt in terms of policy impact, but Page masterfully proves her point that simply by having the ear of two presidents (and one presidential candidate) in careers that spanned from Reagan to Trump offered her the opportunity to influence policy and political strategy.

Bush was more than an acid-tongued truth-teller or white-haired grandmotherly figure. From HIV/AIDS to Cold War diplomacy to the 2003 Iraq invasion to political score-keeping to character-judging, the first lady held forth with her husband, sons, senior government officials and foreign dignitaries. Like the arc of her life itself, she created a bridge for first ladies that reached from traditional feminine pursuits to modern feminism. This definitive biography is a welcome contribution to our understanding of the complex role of presidential spouses.

The Matriarch

Barbara Bush and the Making of an American Dynasty

By Susan Page

418 pp. $32.50