Ever since poker began moving up from New Orleans on Mississippi River steamboats about 200 years ago, newspaper and dictionary editors as well as military, business and political chroniclers have tended to devalue its cultural currency or ignore it altogether. They've often done so in the face of abundant evidence that playing poker helped numerous American movers and shakers make their way in the world.

For 19th-century figures like the statesman Henry Clay, Sheriffs Bill Hickok and Pat Garrett, and Generals William Tecumseh Sherman, John Bell Hood and Ulysses S. Grant, poker was essential to the development of their education, bankroll and modus operandi.

Why try to scrub poker from history, then? Because playing the game wasn't virtuous. It involved gambling, for one thing, often in combination with hard liquor, foul cigars, loose women and concealed weapons. You either lost money or took other people's -- not by hard, honest toil, but by cunning and ruthlessness. Even worse was that during its earliest decades, poker was accurately called the Cheater's Game. (In addition to bowie knives, the Will & Finck Company in San Francisco did booming business in card-hiding devices that strapped to one's forearm and were worn under sleeves with extra-wide cuffs.) Bret Harte and Mark Twain tuned in to poker's pleasures and downside, but until John Dos Passos' ''U.S.A.'' trilogy in the 1930's, most serious writers did not.

Even in the swirling American mainstream, the two main currents of our heritage have kept to a parallel course. The risk-averse Puritan work ethic has carried us at least as far as the frontiersman's urge to light out and seize the big chance; in tandem, they've made us who we are.

Yet proponents of each side did not like to credit the other with anything positive. Huggers of the shore don't praise daredevils; gold rush or riverboat gamblers remain unimpressed by those who husband savings accounts.

The habit of sweeping poker under a carpet of virtue persisted through much of the 20th century. But in his 1970 book ''Nixon Agonistes,'' the historian Garry Wills showed how ''vices'' like poker could, in the right hands, become telling probes into the heart and mind of an officer or a president, even a Quaker like Richard M. Nixon, who was very much a product of the Puritan ethos.

Wills also showed that while Nixon played ruthlessly as a lieutenant in the Navy, Gen. Dwight Eisenhower was even better at poker, perhaps because he played with more joy -- and with a stricter sense of virtue to boot.

''Like Nixon, he made large sums of money in the long games at military bases,'' Wills wrote. ''Unlike Nixon, he was so good he had to stop playing with enlisted men; he was leaving too many of them broke.''

Even so, when Eisenhower chose Nixon as his running mate in 1952, both men stopped playing or even mentioning poker, fearing voters would think it unsavory.

Harry Truman, the man Eisenhower replaced in the White House, was lucky enough to have a biographer, David McCullough, who followed Wills's lead, though with quite a bit more affection for his subject. McCullough's definitive 1,120-page ''Truman'' (1992) sympathetically teased out the more untoward elements in Truman's development as an artillery officer in World War I, and later as a businessman, judge and politician. His book not only mentions poker 34 times, but it also clarifies how playing the game defined Truman, perhaps our most mainstream president.

''He never learned to play golf or tennis, never belonged to a country club,'' McCullough wrote. ''Poker was his game, not bridge or mah-jongg.'' Truman's Monday night sessions with old Army buddies ''had a 10-cent limit. A little beer or bourbon was consumed, Prohibition notwithstanding, and the conversation usually turned to politics. Such was the social life of Judge Harry Truman in the early 1930's, the worst of the Depression, years when Adolf Hitler was rising to power and Japan invaded Manchuria.''

Truman's preference for poker over fussier games helps explain the temperament of ''Give 'Em Hell Harry'' as commander in chief during wars with Japan and Korea, as well as at the dawn of the Cold War.

Revealing as these biographies are, sometimes outsiders can see American traits even more clearly than we see them ourselves. The Hungarian historian John Lukacs, for example, called poker ''the game closest to the Western conception of life where men are considered moral agents, and where -- at least in the short run -- the important thing is not what happens but what people think happens.''

Our keenest observer, Alexis de Tocqueville, wrote in ''Democracy in America'' (1840): ''Those living in the instability of a democracy have the constant image of chance before them, and, in the end, they come to like all those projects in which chance plays a part.'' This was true, he deduced, ''not only because of the promise of profit but because they like the emotions evoked.''

It is unclear which gambling games Tocqueville witnessed, but he came to appreciate our allegiance to chance while traveling in 1831 aboard the steamboat Louisville on Twain's Mississippi, the original American mainstream.

Photo: President Harry S. Truman, center, played poker with friends aboard the U.S.S. Williamsburg in 1949. (Photo by Truman Library)