Henry Montoya of Denver shows up regularly every two years at his precinct polling place, signs the register, goes behind the curtain--and pushes the exit button, leaving not a mark on the voting machine. It is his way of protesting a political system that persistently, he says, offers "no one worth my vote."

Montoya is one of many fascinating characters who inhabit a new paperback, "Nonvoters: America's No Shows," by two professors at Northwestern University's Medill School of Journalism, Jack C. Doppelt and Ellen Shearer (Sage Publications).

His is an extreme case, because most election dropouts are literally no-shows. They don't cast ballots, even if they are registered to vote. And, as Doppelt and Shearer point out, they tend to be equally invisible in the political debate, as both candidates and pollsters focus on the attitudes of likely voters.

But that doesn't mean election dropouts are unimportant. They slightly outnumbered those who voted in the last presidential election and are vastly more numerous than those who chose the members of Congress and governors elected in 1998. They are "the other America," the one that has abandoned one of the basic privileges and responsibilities of citizenship. Their indifference and hostility pose a clear danger to the health of the American republic.

The two professors and their graduate students investigated these folks through a 1996 pre-election questionnaire and a large number of follow-up interviews.

To jump to the bottom line, the authors offer no prescriptions for enthusing the nonvoters about the joy of voting and no optimism that the steady decline in turnout over the past four decades will be easily reversed. "It may take decades for nonvoters to change their attitudes and beliefs, to find heroes in the political world and meaning in government actions or responses," they write. "Certainly it will take years for nonvoters to receive information from the political process with more than passing curiosity or hostile cynicism, much less to act on it by voting. The disconnect is enormous, the conviction to snub the polling place ingrained."

If their volume offers little in the way of hope, it is rich in insights. Conventional wisdom is that nonvoters are people who are "turned off" to politics, meaning that they are either alienated from it or uninformed. They're supposed to be mainly people with minimal educations and incomes.

Doppelt and Shearer find that only about one-quarter of the nonvoters fit into the categories their students labeled "Don't Knows" and "Alienated." These two groups are lacking in schooling and money; they are mainly older--over 45--and, in the first group, predominantly female. And of course they either don't know much about politics or believe it makes no difference to them.

The other categories are not what we typically think. The most numerous--3 out of 10--are "Doers," mainly young, well-educated, avid consumers of political news and actively involved in their communities. Not voting is a deliberate choice for them, justified in their minds because they "view their vote as a negative tool to be used to fix a political problem or change a bad situation, rather than as a measure of civic responsibility." If they vote, it is usually to get rid of someone; so their passivity possibly can be taken as a sign of contentment.

The next largest group, the "Unpluggeds," are also young, but they are the opposite of the Doers--poorly educated, separated from sources of political information and inclined to assume that elections won't affect their lives.

Finally there are the "Irritables," the second-oldest category, with relatively good incomes and education and big consumers of political news. But what they learn aggravates them. They express great anger with politicians in general and Congress in particular. They love term limits.

And they are receptive to talk of a third party.

The gloomy message of this book is that longer voting hours, easier access to absentee ballots or even Election Day registration might not do much to increase participation rates.

The authors say of the nonvoters: "Behind the answer that they are too busy to vote or that the process is too cumbersome lies the accumulated belief of a majority of Americans that a vote has not only lost its actual value in terms of influencing the result of an election . . . but also its symbolic value as a democratic virtue. . . . The vast majority of nonvoters are not turned off by a particular candidate or a certain election. They opted out long ago and are beyond the reach of conventional measures to bring them back."