IT'S HARD TO BELIEVE that all of the people who have taken part in political demonstrations since Ronald Reagan's election actually live in the same country. Last September 19, 300,000 labor unionists and civil rights activists hit the streets on Solidarity Day to oppose Reagan's budget cutbacks. In March, thousands of Republican realtors swarmed over Capitol Hill to demand a balanced federal budget and lower interest rates. On June 12, 750,000 of the nation's well-educated middle class descended upon New York to urge an end to the nuclear arms race. And this summer, a much smaller but decidedly more gleeful throng of conservatives danced on the grave of the Equal Rights Amendment at a gala Washington bash.

What is perhaps most astonishing is that the rising political discontent in so many quarters of American society comes early in the reign of a president who promised to heal the divisions within the nation by rebuilding the moral, economic and military bases of social consensus.

But in many ways the greatest surprise of all was Reagan's ascendance itself. The New Right's sweeping election victory caught most political analysts flat-footed, and they have been playing explanatory catch-up ball ever since. Now there are at last two provocative books that go a long way toward explaining both the Reagan landslide and the political division that has been its ironic consequence: The New Class War, by leftist political scientists Frances Fox Piven and Richard A. Cloward, and Post-Conservative America, by conservative commentator Kevin Phillips. Both works bear the ideological imprint of their authors; but both are also tough-minded and refreshingly iconoclastic examinations of the social forces that are shaping American politics.

Two more sharply divergent approaches to the same subject would be difficult to imagine. Piven and Cloward argue that politics is the expression of deeper conflicts between economic classes. To this familiar Marxist analysis they add the interesting notion that American history is largely the story of workers using democratic political freedoms to regain the traditional economic subsistence rights wrested away from them by a bourgeois-dominated state. This conflict--"Democracy vs. Capitalism"--eventually produced the Welfare State to protect workers (or "ordinary people," or the "poor" Pivan and Cloward interchange these phrases quite loosely) from the ravages of unemployment and wage cuts. Hence, Piven and Cloward see the Reagan economic and social agenda as simply the most recent big business program for restoring an acceptable brand of social discipline.

But, say, the two political scientists. American voters are not really committed to the laissez-faire precepts of Reaganism. The "moral economy" of the country has shifted unalterably to the presumption that people are entitled to a certain level of state-guaranteed economic protection Reagan's victory was but a "blip" born of disgust with Jimmy Carter's ineptitude. Thus, the stage is set's maybe the curtain rose on Solidarity Day--for the old coalition of labor, Blacks, and the poor to come roaring back into the streets and defend their hard-won economic rights.

Phillips takes a broader historical perspective on the current situation. He portrays post-Vietnam America as a defeated empire in the throes of the fourth major inflationary "Price Revolution" since fuedal times. Much like the people of another economically troubled former empire--Weimer Germany--Americans are anxious, profoundly troubled by a vague sense that their country's moral fiber is unwinding before their eyes. This anxiety is the root of a "radical centrism" among Middle Americans--a revolutionary mood that makes Main Street susceptible to populistic appeals for "decency" and to promises of a mythical good old days restored. Ronald Reagan's skillful campaign rhetoric articulated and capitalized upon the "restorationist" sentiment.

Phillips maintains, however, that the Reagan coalition is inherently unstable. The Sun Belt salesmen, Bible-thumping moralists, Wall Street bankers, neo-conservatives, and disgruntled industrial workers who voted for Reagan in 1980 did so for radically different reasons. To each, Reagan symbolized a different restorationist vision. Because the Reagan romp mobilized so many diverse constituencies--but will fail to satisfy and of them--Phillips foresees its eventual splintering, and a subsequent "dealignment" of American politics and political parties. His only hope for a way out of such a deadlock is for reforms in the political system itself. He believes that America must scrap the outmoded notion of separation of powers and move toward a consensus-oriented parlimentary system.

Despite these differences, both books are in a fundamental sense attempts to answer a single question: Can democracy survive in the United States? It is perhaps the question for the 1980s, made more pressing by the gloomy prognoses of MIT economist Lester Thurow and Harvard's Samuel Huntington, two distinguished scholars who see an American government losing its ability to meet the demands placed upon it by various segments of society. Piven and Cloward, who see democracy principally as a means for working class advances, answer a tentative "yes" to this question when they predict a new mass movement for redistribution of power and wealth.

But this is a rather narrow and altogether too optimistic forecast. As Phillips recognizes, there are other groups at large on the political scene now, using their democratic freedoms for ends Piven and Cloward will never consider progressive. Mass political participation produced Martin Luther King--but also Howard Jarvis, George Wallace, and Jerry Falwell. To put it another way, Piven and Cloward correctly assess the contradiction between capitalism and democracy: Phillips, however, paints a subtler picture of an America bedeviled by multiple contradictions--regional, cultural, racial, religious, and ideological. Nowhere is this basic flaw in their analysis more evident than in Piven and Cloward's dismissal of Reagan's appeal to "traditional values" as a corporate ruse. Rather, Reaganism is a very real evocation of long-standing American right-populist political sentiment.

SUPPLY SIDE ECONOMICS was the key to restoring prosperity--and hence political consensus--under a Reaganite new order. In the wake of its failure, the prospects are indeed that the American political system will come slightly unhinged, and that deadlock will be the result. Despite the approaching confusion, a plausibly discernible set of new battle lines are emerging. One is the old class boundary noted by Piven and Cloward. Both Wall Street and organized labor seem to be solidifying old ties to their respective traditional parties, the Republicans and the Democrats.

But the New Right constituency is unlikely to feel at home in either of these parties. It may yet seek accomodation, but it may also try to form a new party of true believers. Richard Viguerie has often talked about doing just that; now he has the money, the organization, and the mailing list to pull it off. And the latest Conservative Digest, published by Viguerie, is a non-stop tirade against big business influence on the Reagan Administration. Finally, a smaller fourth bloc may emerge from among "lifestyle liberals"--the young professionals and intellectuals who voted for John Anderson in 1980 and who are the backbone of the grassroots nuclear freeze movement. Anderson hasn't yet denied interest in the 1984 race.

So much is speculation. The less dynamic--and more likely--prospect is for a prolonged political deadlock punctuated by outbursts of popular unrest and made-to-order "movements" centered on the "new ideas" of youthful-looking congressmen and senators. In a decade of Thurowian "zero-sum" economics, American democracy seems capable of fostering only division, not consensus--and certainly not a consensus behind the kind of progressive environmental and economic reforms that the country needs most. Basic changes in the political system--moves toward parliamentarism--are even more unlikely. We will be lucky indeed if America manages to avoid the kind of "escape for freedom" a la Weimar that Phillips forecasts in his more lugubrious moments. Still, if there is any hope to be found in this otherwise dismal picture, it lies in the fact that none of the major organized constituencies--including the New Right--is openly advocating an authoritarian "escape." It remains to be seen if this shared democratic commitment can survive the frustrations that democracy itself promises to produce in the coming years.