THE odds in the presidential sweepstakes have become so lopsided in recent months that black humor has replaced partisan arguments as the conversational currency of this pre-campaign season. The only way to elect a Democratic president, suggest some wags, is for the Democrats themselves to nominate George Bush. Others propose simply canceling the election and scheduling a coronation instead. Most mordantly of all, a recent New Yorker cartoon pictures a bloke at a bar pounding his fist on the counter, defiantly declaring, "Anybody who doesn't like our one-party system can go to Russia!" It is taken as a foregone conclusion that George Bush is simply unbeatable. Democratic politicians are so intimidated by the president's aura of invincibility and his well-proven instinct for the jugular that not one of the party figures widely considered a front-runner has consented to run, fearing not only defeat but humiliation at the hands of a masterfully manipulative Republican campaign machine. Those few who dare to run - Tsongas, Wilder, and Harkin as of now, Clinton, Kerrey, and Brown likely to follow - are so little known to most Americans that they are dismissed in advance as mere sacrificial lambs. Is this virtual absence of opposition a healthy development for American democracy? Are we so much in agreement about this nation's proper priorities that we don't need an opposition to test the truth of our consensus? For what they are worth (and it may be less than we think), polls reveal the same puzzling pattern they have shown for the past decade - an apparent endorsement of the president as an individual and a simultaneous rejection of many of his particular policies. Does Bush's popularity reflect not trust in the man so much as a desire to keep hearing his reassuring if misleading messages that "We're No. 1!" and we needn't change our policies or habits to accommodate a changing world? Could it also be that many of those who reject his policies have simply dropped out of politics altogether in the despairing belief that it has become irredeemably corrupt? While many pros have simply abandoned the playing field to a seemingly invincible opponent, a few rank amateurs sense that the moment is ripe for a much bolder strategy. Free of the constraints of party politics, these individuals are intent on broadening the debate and reopening options that an increasingly intolerant political climate has foreclosed. Tom Laughlin, known as "Billy Jack" from a '70s film by the same name, has established what he calls "The American Voter Revolt of 1992." "Voters' anger and sense of being left out of the political process is much deeper and more explosive than I had ever imagined," he observed after canvassing in Iowa. Harking back to the film "Field of Dreams," he sums up his strategy: "If you build the crowds, he will come. [If] those people who would like to [run] but don't believe there's a chance [of winning] start to see a powerful grassroots movement, then indeed their courage will be found." Equally quixotic - or perhaps prescient - is Larry Agran, the innovative former mayor of Irvine, Calif., where despite his liberal inclinations he consistently won elections in the birthplace of Reaganite conservatism, Orange County. Mr. Agran is a longtime advocate of "municipal foreign policies," strategies by which cities have sought to compensate for a perceived lack of positive policies by the federal government by establishing overseas programs of their own at the local level. In a radical departur e from the boundaries of permissible debate, Agran proposes to pare the military budget in half (to $150 billion), withdraw all US forces from Japan and Europe by 1995, and redirect the savings to local and state governments for education, health, housing, nutrition, and environmental rescue, as well as to deficit reduction and retraining workers displaced by cutbacks in military spending. Sensible policies all, though unlikely to get Agran elected. Yet at this juncture, just to suggest such dramatic policy shifts in the public forum of a presidential campaign is a service to the nation. Even those who disagree with the proposals of these mavericks should welcome the renewal of the vigorous debate on which a healthy democratic process depends. For without a greatly broadened and deepened debate, American politics may soon come uncomfortably close to resembling the dynamics of the one-party states we so strenuously abjure. And by then, we won't be laughing so hard at the bloke in the bar.