The adroit author (Open Net, 1987, etc.), Paris Review editor, and amateur jock who plays with the pros suits up once again to pitch horseshoes with George Bush and, incidentally, to pursue the elusive factor that makes champions out of mortals. Originally concocted a few years ago as a Whittle Communications advertising-supported giveaway, the text has been updated to acknowledge the Bush defeat in 1992, ``perhaps diminishing him as an avatar of the X Factor'' but not at all reducing the homage the author (a Democrat) pays his horseshoe opponent as A Swell Guy. Defeated once by then-president-elect Bush, Plimpton, before a return match, seeks the athletes' grail, the sovereign ingredient that produces winners. The teachings of an occasional Wall Street mogul like Henry Kravis and of a lot of sports figures, from Red Auerbach and Bill Russell to the sainted Vince Lombardi, are trotted out to raise the reader's diastolic and systolic pressures and to pump up the eager acolyte. Even as he essays his version of the usually plebeian self-help manual, the patrician persona of Plimpton, scion of the upper crust, is maintained. How could it be otherwise, with tales of the local yacht club tennis tournament and his grandparents' tennis court (where, at age eight, he was heckled by a parrot)? The coaches' pep talks and the country club locker room badinage may or may not aid the hoi polloi aching to enter ``the zone'' where no move is false- -it didn't help the author in his Camp David rematch with President Bush; he lost again. Win or lose, Plimpton writes with self-effacing humor and at least as much wit as wisdom; America's most famous professional dilettante doesn't demand to be taken too seriously.