Nine years ago, Ruth Messinger's public life lay in wreckage. Her ascent through the decades from a community activist on the Upper West Side to the borough president of Manhattan to the Democratic candidate for mayor in an overwhelmingly Democratic city had culminated in not one but two humiliations. The first was having to fight the Rev. Al Sharpton, unapologetic architect of the Tawana Brawley bias-crime hoax, for the Democratic ballot line. The second, having survived Sharpton, was running against Rudolph Giuliani, an incumbent at the apogee of both his popularity and arrogance. Messinger finished nearly 20 percent behind Giuliani in the 1997 vote, and as City Hall passed four years later to another Republican, Michael Bloomberg, Messinger's party looked either to Hispanics or more centrist whites as their electoral prospects for the future. It is not too much to say, however, that American Jewry may be better and more vital as a result. With one lengthy chapter in her career slammed close, Messinger opened another in 1998, becoming president of American Jewish World Service, an organization that in a Peace Corps sort of way sends young volunteers to provide humanitarian aid and technical assistance in the developing world. Most recently, Messinger emerged as one of the signal forces behind the Darfur issue in the United States, particularly mobilizing Jews. The recent rally in Washington, which drew tens of thousands to protest the genocide of the Arab janjaweed militias against African Muslims, offered a very public confirmation of Messinger's advocacy efforts in countless speeches, conferences and essays. In doing this, Messinger has pumped some desperately needed purpose and vigor into the unaffiliated and secular portions of American Jewry. From the 1880s through the 1960s, these were the most vital elements of the population, bristling with activism on labor issues, Zionism and civil rights. The religious leaders who entered such frays were often following the lead of the nonobservant. ENTERING THE 21st century, the crusades of the past can nourish nostalgia but not provide identity. Labor organizing matters relatively little to a Jewish community well situated in management and professions. The legal battles of civil rights were won so long ago they are literally the stuff of history classes to high school and college students. The Lebanon invasion and two intifadas made Zionism a trickier proposition for Jews on the Left. At the most perverse extreme, some of them sought to express their Jewish concern with social justice by mouthing the anti-Israel rhetoric of groups such as the International Solidarity Movement, United For Peace and Justice, and Jews Against The Occupation, as if self-abnegation were the highest form of self-affirmation. Unlike secular Israelis - whose Jewishness is incidentally reified by the Hebrew language, IDF service, the use of religious texts in state schools, and the conflation of the sacred and civil calendars - America's secular Jews have lost many of the meaningful, substantial bases of peoplehood. It is unrealistic to expect religious observance to fill the gap, for American Jews have always been divided between atheists and believers. Yet it is also ridiculous to pretend that bagels and Curb Your Enthusiasm, or even Heeb and Jewlicious, can offer anything more than what the sociologist Herbet Gans famously called "symbolic ethnicity." The tradition of tikkun olam played such a profound role in Jewishness because it applied a distinctly Judaic theology in an unparochial way. It reconciled the warring Jewish impulses toward tribalism and universalism by saying that universalism was a consummate act of tribal fealty. MORE PERHAPS than any figure on the American Jewish scene today, Messinger has found a way to modernize the appeal, to stir Jewish idealism in a cynical age, and to even make it cool. Her background in the grassroots politics of the Upper West Side has given her a talent for individual persuasion and personal connection. And one senses, hearing Messinger address a roomful of students or their parents, that this current mission has returned her to some essential, overtly Jewish aspect of herself. It is fair and right to wonder what will happen when Messinger someday leaves the American Jewish World Service. Cachet fades, especially when it rests on one charismatic figure. Just think about the standing of Michael Lerner of Tikkun, not so many years ago the guru of Hillary Clinton and cover boy of The New York Times Magazine, with his self-proclaimed "politics of meaning." Ruth Messinger's greatest legacy will be to train prot g s and inspire imitators, so the lessons of her present success long outlast her. The writer is a professor of journalism at Columbia University and an author, most recently of Letters To A Young Journalist.