One girl raised her hand to ask: “How did you get to be president?” The First Lady demurred and said she just married one. That night she and the president she married went to dinner at a Tex-Mex place in Arlington, Va.–a signal to America that life should get back to normal.

The day was a taste of things to come. Before Sept. 11, she was headed for perhaps the quietest First Ladyship since Bess Truman’s. Now that’s changed. First Ladies have often played important roles–private and public–during national crises, and Mrs. Bush is likely to follow that pattern. My study of First Couples suggests that great challenges profoundly alter marriages and public images in the crucible of the presidency. Some, like Woodrow and Edith Wilson and Richard and Pat Nixon, are virtually crushed by the pressure. In others the First Lady emerges as a pillar of support for a beleaguered husband–and becomes a national figure in her own right. Mrs. Bush’s initial approach to her role–she had hoped to lead a tranquil life in the White House–is no longer possible. The country’s expectations and needs have changed, and so, too, have the president’s. And it is likely that the personal strengths she has long brought to her marriage–steadiness and calm–will help both her husband and her country.

In responding to a national emergency, the president and First Lady can learn from their predecessors, especially the Roosevelts. Eleanor became FDR’s legs, ears and eyes. On a trip to England she experienced the nightly pounding of the Luftwaffe. Walking through bombed-out factories and hospitals and visiting the troops, she stood in for her wheelchair-bound husband. She was the administration’s moral voice, pushing for African-Americans to be fully integrated into the armed forces, going down into coal mines, urging her husband to do something about the horror engulfing Europe’s Jews. “I do not know what we can do to save the Jews in Europe,” she wrote in her daily column, “but I know that we will be the sufferers if we let great wrongs occur without exerting ourselves to correct them.”

During the Cuban missile crisis, JFK urged Jackie and their children to move to a secret underground shelter outside Washington. With her keen sense of history, Mrs. Kennedy refused. “At night after long hours of secret planning,” correspondent Hugh Sidey wrote, “Kennedy would walk alone on the grounds of the White House trying to clear his mind. Jackie would walk out to meet him and the two would go back inside for dinner, where he would tell her everything that was happening.” When the danger was over, the president presented silver calendars to his key advisers with the 13 days of the October crisis marked off, and gave Jackie one, too.

During Vietnam, Lady Bird Johnson kept vigil with her sleepless husband. The black mood Mrs. Johnson called “the miasma” hung over the final two and a half years of the Johnson presidency, but the First Lady never lost her composure, or her ability to temper her husband’s excesses. In 1968 Lady Bird helped to convince him that it was time to give up his life’s greatest love, and as he prepared to announce a bombing halt and the end of his political life, she whispered in his ear, “Remember, Lyndon, pacing and drama.” As he reached the surprise ending, he looked off camera for a moment–at Lady Bird.

This is not the presidency either George W. or Laura Bush envisioned. He wanted to shrink government and keep the prosperity going, while, in her own words, she would do, as she always has, “what really traditional women do.” Those plans, like so much else in recent days, are irrevocably changed.

In private, the ways in which Laura has been a rock for George will be as important as ever as she keeps him centered and focused. And in public, the woman who helped her husband quit drinking and settle down so long ago will be indispensable in reminding Americans that the “normal” things in life matter: children, family and church. Now the president and First Lady will be judged on a more demanding scale: how they perform as leaders–co-leaders–of a nation at war.