Wallace, in 1962. During the New Deal, as Secretary of Agriculture, he helped restore order to the farm business. Photograph by Slim Aarons / Getty

“Meet the new Assistant President,” James Reston wrote, in the Times, in October, 1941. “His decisions in the next few months or years will undoubtedly affect your job, your rent, and the price of your groceries. And, what’s more important, his decisions may determine the outcome of the war and the basis of the peace.” Reston was describing Vice-President Henry Wallace, the farmer-intellectual from Iowa, who had taken charge of economic planning on the eve of America’s entry into the Second World War. Wallace’s Washington career had begun just eight years earlier, when Roosevelt appointed him Secretary of Agriculture. Disciplined and visionary in equal measure, Wallace had established himself as one of the stars of the New Deal, helping to restore order to the farm business. He was also considered something of an oddball: insiders mocked his fascination with plant genetics and gossiped about his enthusiasm for Nicholas Roerich, a Russian painter turned Theosophical guru. Nonetheless, Roosevelt’s faith in Wallace gave him stature. One adviser implied that Wallace had been picked as Roosevelt’s running mate in 1940 not because he supplied a political advantage but because the ailing President saw him as a worthy successor.

Others in the Roosevelt circle took a much dimmer view of the idiosyncrasies of the “Assistant President”—his righteous liberal crusades, his distaste for machine politics, his pro-Soviet leanings. The President agreed, with some ambivalence, that he should be dropped from the 1944 ticket. Still, a Gallup poll showed that Wallace was by far the most popular of the Democratic candidates, and at the Democratic Convention that year he came close to defeating the Party bosses’ choice, Harry Truman. On the second day of the Convention, there was a huge pro-Wallace demonstration; Claude Pepper, the Florida senator, later said that if he had managed to place Wallace’s name into nomination that evening the Vice-President would have kept his position—and become President upon Roosevelt’s death. When Pepper was only a few steps from the lectern, Party leaders succeeded in having the session adjourned. The next day, the nomination went to Truman. Four years later, Wallace launched a rancorous third-party campaign against Truman, effectively destroying his own reputation.

With the exception of Al Gore, Wallace remains the most famous almost-President in American history. In the past half-century, progressives have often dreamed of a world in which Wallace re-started the New Deal and curtailed the national-security state. The latest iteration of this fantasy appeared in Oliver Stone’s “Untold History of the United States,” a documentary series that ran on Showtime last fall and produced a companion book, by Stone and Peter Kuznick. “There might have been no atomic bombings, no nuclear arms race, and no Cold War,” they write. For conservative historians, however, and for quite a few moderate liberals as well, a putative Wallace Presidency is an end-times scenario of appeasement and Communist infiltration. Thomas W. Devine’s new book, “Henry Wallace’s 1948 Presidential Campaign and the Future of Postwar Liberalism” (North Carolina), portrays him not as a crucified savior or a demon of subversion but as a tragically flawed figure in whom idealistic conviction went sour. All commentators would agree that Wallace was one of the most curious characters ever to have come within a heartbeat of the Presidency.

With an oblong face, a thick shock of gray hair, and a starchy voice, Wallace resembled a pillar of Washington rectitude from a Hollywood drama. When Time put him on the cover, in 1940, it had Grant Wood execute his portrait. Yet “oddball” is the right word. Wallace refused alcohol, experimented with diets (including a milk-and-popcorn regimen), walked all over the city at an exhausting pace, and threw himself into sports and fads. Despite his vibrant physical presence, he was reserved, at times debilitatingly shy, and inept at small talk. John Culver and John Hyde, in their hagiographic but mesmerizing 2000 biography, neatly summed him up with their title: “American Dreamer.”

Wallace came from a noted Iowa family. His paternal grandfather and his father, both also named Henry Wallace, together founded an influential farm journal, which remains a going concern; since 1898, it has been known as Wallaces’ Farmer. The Wallaces were independent-minded Republicans, assiduously cultivated by national Party leaders. In 1921, President Warren G. Harding picked Wallace’s father to be the Secretary of Agriculture, and he remained in that post until his death, in 1924. While the rest of the economy boomed, farmers were enduring a prolonged crisis, with surpluses accumulating and prices plunging. The elder Wallace pleaded, in vain, for government intervention, and grew disillusioned with his party’s handling of farm issues.

The third Henry Wallace was born in 1888, and grew up first on a farm and later in Des Moines. He studied agriculture at Iowa State, his senior thesis devoted to the topic of soil conservation. In 1914, he married Ilo Browne, a fashionable woman of considerable means. At first, he seemed content to write editorials for Wallaces’ Farmer, peruse mystical literature, and undertake agricultural research. He thought that he could increase corn crops by cross-breeding and inbreeding, and in 1922, working with a Chinese strain and one supplied by the plant geneticist Donald Jones, he developed what became the first commercially successful hybrid corn. Soon, with the help of Ilo’s money, he started Pioneer Hi-Bred, a hybrid-seed company. After the death of his father, Wallace became a national farm authority by default. Herbert Hoover had long been a family enemy, and when F.D.R. challenged Hoover, in 1932, he turned to Wallace for guidance. The next year, Roosevelt was in the White House, and Wallace took his father’s old job at Agriculture.

The Great Depression and its aftermath brought out the best in Wallace. Endowed with emergency powers, he regulated prices and bought up surpluses. His methods verged on the Draconian—at one point, he ordered a mass slaughter of piglets—yet skeptics grudgingly admitted that he had righted a desperate sector of the economy. Although conservatives on the Supreme Court overturned much of his farm policy, he showed political cunning in fostering substitute legislation. As the New Deal lost momentum, Wallace became its most forceful defender. At the same time, he anticipated problems that were not yet on many people’s minds. In 1936, he wrote, “Probably the most damaging indictment that can be made of the capitalistic system is the way in which its emphasis on unfettered individualism results in exploitation of natural resources in a manner to destroy the physical foundations of national longevity.”

Wallace’s mystical propensities now had national ramifications. One day, he became fascinated by the pyramid-with-an-eye figure that appeared on the American seal, and proposed that it be incorporated into the national currency. Roosevelt had it placed on the dollar bill, where it remains, to the delight of college stoners. In 1929, Wallace met Nicholas Roerich, who first made his name as a painter in the Symbolist vein. In artistic circles, he is remembered chiefly for having co-written the scenario of, and created the sets for, Stravinsky’s “Rite of Spring.” In the twenties, Roerich and his wife, Helena, blended aspects of Theosophy, Hinduism, and Tibetan Buddhism into a doctrine called Agni Yoga, which was presented in such treatises as “Fiery Stronghold” and “Flame in Chalice.” (You can examine copies at the Roerich Museum, on West 107th Street, in Manhattan.) Wallace diligently studied Roerich’s writings and wrote to him in terms such as these: