After three weeks of flagellation by a phantom sex expose, the vaunted campaign organization of a furious George Bush panicked in dealing with the bizarre reality of post-Hart presidential politics.

The tight little world of politics -- a few hundred politicians and news people -- has been agog all month. Its inhabitants have frolicked in one wave after another of rumors, not really about alleged extramarital affairs by the allegedly strait-laced vice president but about alleged forthcoming news accounts of the alleged affairs. There is no evidence to confirm the existence of any such accounts, much less raw data or juicy tidbits.

All this would have remained secret for millions of real Americans who in the summer of '87 are not immersed in '88 presidential politics -- or it would have but for the reaction of Bush's own campaign. By volunteering a ''no'' answer to the ''Big A'' (for adultery) question, the vice president's men unwittingly opened the sluice gates for publication of the nonstory. It also suggests that bad blood may be a fixture in Bush's coming war for the nomination with Sen. Robert J. Dole.

Bush is too well organized, too well financed and too much the favorite of establishment Republicans to be seriously damaged by the flap. But it does cast doubt on his campaign team's overreaction to crisis. It also suggests the kind of crisis that may become commonplace in the wake of Gary Hart.

Telephone calls poured into the Bush campaign headquarters the week of June 1 about imminent publication (the New York Post and Daily News were mentioned first, but the list grew each day) about supposed vice presidential hanky-panky. The vagueness of the reports, with no fewer than three women presumed to be involved in one account or another, suggested either mistaken identity with Don Juan or Casanova -- or an unfunny hoax.

The waves abated, then resumed June 17 when Chicago Sun-Times gossip columnist Michael Sneed reported that ''several major newspapers are sifting . . . reputed dalliances'' of ''Mr. Boring.'' Worried Bush backers, including nine congressmen, hastily telephoned to ask what in the world was happening to their candidate.

Republican sources said Bush campaign manager Lee Atwater fingered Dole adviser David Keene (Bush's No. 2 operative in the 1980 campaign) as the rumormonger. An enraged Keene tried to get through to Bush himself with his flat denial, but the vice president did not take the call.

At this point, only brief, unexplicit items about Bush had appeared in print. But word raced through the political underground railway -- spread, to be sure, by some Dole partisans around the country, but by many others as well. At week's end, Rich Bond, the vice president's brilliant but excitable political organizer, telephoned Keene to accuse Dole forces of a centralized, fully coordinated smear campaign.

Atwater and the rest of the Bush high command, convinced that the rumors would soon be published, reacted in a way that spelled panic to friends and foes alike. George Bush Jr., a key campaign adviser, quietly informed Newsweek that his father's ''answer to the Big A question is N.O.''

Publication of that statement in Newsweek's Periscope section opened the floodgate. What had been limited to inside-the-Beltway gossip became publishable news, attributed to the magazine. Thus was it revealed to the public. The vice president himself fumed, kept silent and expressed the private opinion that his son and staff would have been well advised to follow his example.

No one with intimate and direct access to facts believes that any newspaper, magazine or network ever had any expose' ready for publication. That this ugly and prurient chimera could engage the political community for the better part of a month is Gary Hart's unwanted legacy. For the Bush campaign leviathan to panic suggests the need for fine-tuning in the front-runner's fabled machine.