BOOK REVIEW / NONFICTION : A Lone Voice of Reason and Compassion : REASON TO BELIEVE <i> by Mario Cuomo</i> ; Simon & Schuster $21, 182 pages

Who will pick up the fallen banner of American liberalism in an era when a Democratic president refuses to utter the “L” word and Republican congressional activists employ it as a kind of curse?

Well, Mario Cuomo, former governor of New York and perhaps the last hope for New Deal liberalism, makes a heartfelt effort to vindicate the idea of progressive politics in “Reason to Believe.” But, significantly, even the otherwise plain-spoken Cuomo is coy about attaching the label of liberalism to his manifesto.

Cuomo, who felt the sting of the Republican backlash in 1994, is compelled to acknowledge the hard realities that beset the Democratic Party in general and liberalism in particular.

“As one who had been capsized by the Republican tide . . . I was hoping that a great chorus of voices would rise up to say what seemed to me so clear,” he writes. “The chorus, however, has been slow to assemble.”

So Cuomo offers himself as a lone voice in the wilderness, an advocate of reason and compassion rather than what he characterizes as “the New Harshness” of a firebrand like Newt Gingrich and his Republican cohorts.

“Outrage is cheap, easy and oversold,” Cuomo argues. “The nation needs less anger and more thoughtful reflection, less shouting and more listening, less dissembling and more honesty.”

Cuomo does not deny that the electorate is “disenchanted” with the perceived failure of social welfare programs dating to the New Deal--but he insists that a return to society based on “rugged individualism” will do nothing at all to address the crisis of poverty, violence and despair in America.

“From our economy to our culture, we are facing problems that are big, awkward, expensive, even repugnant,” Cuomo writes. “They will never get better if we pretend they don’t exist or insist they’re not our responsibility. And they will never quiet down if we just shout at them to shut up.”

What will work? The essential message of Cuomo’s book--and, in a sense, the best definition of liberalism in American politics--is that “we’re all in this together.” His credo, which he attributes to his late mother, is simple and decent: “In helping one another, we almost always help ourselves.”

Nor does Cuomo concede the moral high ground of “family values” to the conservatives. He agrees that we ought to promote the values of “hard work, humility, self-sacrifice and persistence,” and he calls on us to “envelop [our children] in the warmth of our national ideas.”

According to one of Cuomo’s more grandiose (and, I’m afraid, antiquated) proposals, the moral climate of America can be improved through a government-funded television advertising campaign to promote “the wonder of life, the beauty of our democracy, the power of hard work and aspiration.”

“If we do it right, our children might finally believe that we mean what we say about family values,” Cuomo writes, “because we will have demonstrated conclusively that we value the family of America.”

Indeed, Cuomo appeals to our altruism, if any such notion actually exists in American politics nowadays, in arguing for a social safety net that cushions the fall of the downwardly mobile. But his more compelling argument owes nothing at all to good intentions; the American Dream is beyond the grasp of even the so-called middle class, he points out, and even the affluent have something to fear from the growing “underclass” of the poor and the powerless.

“Even if your two-parent family is safely ensconced in the suburbs, happily employed, financially comfortable, well-educated, well-insured, young, healthy, able, and free of drugs,” writes Cuomo in an ironic (if not plainly sarcastic) flourish, “it’s in your self-interest for government to help those people who are not as lucky as you.”

Cuomo’s book--rather like the man himself--is earnest, sometimes downright sentimental, full of both high ideals and practical ideas, and leavened with a bit of self-effacing humor: “It just may be the only book in print on America’s social and political situation,” Cuomo quips, “that neither quotes, cites, nor purports to paraphrase Alexis de Tocqueville.”

Still, Cuomo is mostly preaching to the choir in “Reason to Believe,” and one wonders whether a single soft-spoken voice, no matter how articulate and appealing, will be heard at all in a political environment that has come to resemble one vast talk-radio hate-fest.