A striking feature of The Power Broker, which resulted from 522 interviews, was the staggering amount of research that went into it, a fact that is true for all of Caro’s books, including Master of the Senate. If the books are remarkable in that respect, it is largely because Caro has a secret weapon his wife, Ina Caro, who works as his fulltime researcher. All of his books are dedicated to her, and the inscription for The Path to Power contained an additional line from Shakespeare’s Macbeth: “More is thy due than more than all can pay.”

“Bob is really quite incredible,” Ina Caro said one recent afternoon in their spacious, immaculate apartment overlooking Central Park. A handsome woman in her sixties, with short dark hair, she is witty and imperious, and more articulate than her husband. Reflecting on the way in which Caro has fused scholarship and investigative reporting in his books, she affirms: “He combines them both beautifully, which is really the reason it takes so long,’ How long would it take without her? “It would take an awful lot longer,” she replies, a trace of satisfaction in her voice.

From the start, she was his anchor. Cards advance for The Power Broker was minuscule, so while he worked on the book, she got a job as a substitute teacher to support the family. (They have a grown son, who graduated from Princeton and is now a lawyer.) A historian in her own right—she has a graduate degree in medieval history—she performed thousands of hours of research on The Power Broker, and then typed the two-thousand page manuscript—twice. But the fall range of her talents would not become fully apparent until she and Caro moved to the Texas Hill country in the late 1970s to research the boyhood of Lyndon Johnson; they stayed for three years.

As a young congressman in the 1930s, Johnson harnessed the machinery of the New Deal to bring electrification to his district in central Texas, one of the poorest, most backward regions in the state; it was LBJ’s greatest achievement as a congressman. Caro wanted to know what electricity really meant to the impoverished residents of the Hill Country—especially the beleaguered women—so he sent his wife to interview them. “The women there didn’t want to talk to Bob,” recalls Ina Caro. “He’s a New York male. They were uncomfortable with him. They were more comfortable with me.” The fruit of her labor resulted in The Path to Powers finest chapter, “The Sad Irons” In powerful detail, the chapter brought to life the crushing regimen faced by Hill Country women in the years before electrification—washing, ironing, canning, baking—a regimen that left them stooped and crippled and broken in their thirties, a regimen that called to mind the Middle Ages, or the lives of peasants in Brazil. A writer for Texas Monthly once said “The Sad Irons” may be the “most brilliant single passage of prose ever written about Texas.”

Decades of collaboration have resulted in an ironclad routine for the Caros. She rises early and works on her own books from 5:00 A.hs. to 9:00 A.M. She is the author of The Road from the Past: Traveling through History in France published in 1996 and still in print and is currently working on another historical travelogue about France. Beginning at 9:00, she works a full day for her husband. Ina Caro dislikes doing interviews, but is completely enamored of libraries and archives. For Master of the Senate, she spent protracted amounts of time, by herself, in presidential libraries and archives in Missouri, Kansas, Oklahoma, and Georgia. Then she typed the gargantuan first draft of Master of the Senate, since her husband refuses to write on a computer. (Ina Caro says she has always enjoyed the typing, and that running his words through her own typewriter taught her how to write books herself.)

What explains her dedication? First and foremost is her love of research, but there are other reasons, too. “What really fascinated me historically was how democracy came into being,” she says. “The fragility of democracy fascinates me. ” Her husband’s work touches directly on that theme.

“I felt that what Bob was doing was very important. He makes you understand how democracy works—really works—not how a political scientist says it’s supposed to. And she is obviously enmeshed in her husband’s idealism: “Bob became a reporter because he felt very strongly that the press was the fourth branch of government,” she says. “He felt journalism was a crusade to protect democracy. That sounds corny today, but I think it was deeply felt.”

Scott Sherman is a contributing writer at The Nation and a contributing editor at the Columbia Journalism Review.