THOUGH they are a disparate group cutting across income and class boundaries, the growing number of disaffected American voters shares common ground: They are deeply troubled by their economic prospects and convinced that the present two-party system can do nothing to help them.
This anxiety factor, which pushed a third party to the surface and contributed heavily to the defeat of George Bush in 1992, is even stronger today. Many Americans feel more insecure about their jobs and their ability to provide for their families.
''A larger segment of the middle class - more than ever before - finds itself not only vulnerable but powerless,'' says Sen. Bill Bradley (D) of New Jersey, who along with the popular former Gen. Colin Powell and billionaire Ross Perot is regarded as a possible third-party contender in 1996.
''There is more ferment in the political system today than any time I've been in politics,'' he says. ''People are uncertain ... and they're not going to believe any politician until their own circumstances change.''
Cynicism runs deep, says pollster Andrew Kohut, director of the Times Mirror Center for the People and the Press. According to his most recent poll, President Clinton's disapproval rating of 44 percent is just below the GOP's negative rating of 45 percent. ''We recently asked people who they would vote for if Bill Clinton were running against a Republican or an independent ... some 26 percent said they would vote independent.'' The largest group in the survey, he says, ''are middle-class people who are very anxious.''
Other opinion surveys, conducted by NBC News-Wall Street Journal and CBS-New York Times pollsters, find between 30 and 44 percent of those asked view the economy as ''fairly bad'' and ''very bad,'' and regard unemployment as the nation's most pressing economic problem.
Analysts like Mr. Kohut say many middle-class voters doubt the GOP will come through with any relief, much less the $500 per child tax cuts designed for them. They worry about the impact of budget cuts (that would cut back student loans or push up Medicare payments) on their ability to make ends meet.
LOWER-wage earners fault Democrats for failing to put up a strong fight against the GOP, and lending support to Republican plans to dismantle social-welfare programs. They have seen no follow-through on a pledge Mr. Clinton has repeated throughout his term in office: to boost the wage and skills level of United States workers who are falling further behind.
''The widening gulf in the US economy will increasingly determine our political future,'' says Richard Medley, a professor at Yale University in New Haven, Conn., who also works at the grass-roots level with inner-city youths. He views interest in third-party politics as a sign of desperation, but not resignation. ''People need to feel more secure. A sign that they haven't totally lost faith in government is that they are still looking for answers.''
But while many political analysts doubt that the entrenched two-party system will give way to an independent party's triumph next year, others say there is growing evidence that third parties could receive ample support, with strong economic underpinnings.
''There is anger at the establishment,'' says Norman Ornstein, senior fellow at the Washington-based American Enterprise Institute. ''No job is safe anywhere. You're loyal, but you are easily fired. More and more people are working harder than ever, but their basic lives are fraying at the edges,'' he says.
''They feel enormous pressures, and they are paying more in taxes and getting less for it. There's a sense that Republicans are for the rich and Democrats are for the poor, but who's for the middle class?''
Impressed by voters' support for Mr. Perot in 1992, Kohut thinks there is a much greater chance of an independent candidate succeeding in 1996. While the Texas billionaire's ranks defected largely from the Republican Party, ''the new third-force voters more often have a Democratic pedigree,'' Kohut says.
''They are younger, poorer, and are more likely to be women than were Perot voters,'' he says. Kohut adds that some 40 percent of those who voted in favor of Perot during the last election say they are inclined to pull the lever for an independent candidate in 1996.
But some wonder whether the wide spectrum that constitutes potential strength of third-party support could just as easily be the diversity that weakens it. The blue-collar worker whose wages are eroding may share uncertainty with the middle manager who is a casualty of corporate downsizing, but their different perspectives may keep them apart.
Medley disagrees. ''There is a lot of common ground here,'' he says. ''A lot of these people are tumbling down and landing on top of each other, and they know they need help.''