HE office of the Working Families Party organizer is in a state of disorganization, and has been since he moved in four years ago. Books, files and storage boxes are crammed in a corner, walls are adorned in a style known as basic bare, and the desk has that lived-in look. A campaign poster for Brazil's blue-collar president and a child's drawing provide the only splashes of color.

Dan Cantor's comfort zone rests in his political vision, not furniture; when he recommends fusion, he means cross-endorsement, putting the name of another party's candidate on his party's line, not cross-pollinated food.

What Mr. Cantor, executive director of the party, is organizing from this hardscrabble headquarters in Downtown Brooklyn is a third-party political movement steeped in populist values and — no joke — common decency. It's ideals-are-us politics. As he sees it, Working Families is a new take on a New Deal premise: better public schools, housing and wages. Hampered by a measly $1 million budget, it finds creative ways to raise its visibility. Has to.

Last month it backed a lawsuit that says New York City's voting machines botched the votes of some 60,000 voters, most of them from impoverished or immigrant communities. Last week it decided to field its own candidate, Letitia James, in the race to replace James E. Davis, the city councilman slain at City Hall; that's her working the phones in the next room. (The party had "grown fond" of Mr. Davis, Mr. Cantor says, but could not in good conscience support his brother, Geoffrey). Ideals-are-us, remember?

Mr. Cantor's father, co-owner of a Long Island auto parts store but an off-hours pundit whose guru was Franklin Delano Roosevelt, taught him that mistaking one's own good fortune for virtue is akin to a vice. The lesson stuck. Mr. Cantor thinks the American right is all wrong. "I've been in a rage about this my whole life," he says, "but the form of my response was always — and I think it's a radical response — to try to build a credible political force."

He is strictly a third-party guy: a leftover leftist in sandals, bereft of suit or tie, with a black tee beneath his long-sleeved white shirt. His beard has been downgraded to an intentional stubble that's graying at the edges. He's 48 and has pecked away at politics since he ran for student council president at Gen. Douglas A. MacArthur High School in Levittown with a power-to-the-pupils platform; he keeps a copy around for laughs. Favorite plank: Attendance not required in any study hall.

 
AFTER graduating from Wesleyan University, he did grass-roots organizing in Arkansas (to protest utility rates), and union organizing in New Orleans, got involved in Jesse L. Jackson's 1984 and 1988 presidential campaigns, and, in a brief timeout, worked for a "kind of liberal" private foundation on Long Island. "My heart beats on the left, but I've always tried to be practical as well as ideological," he said. "For someone like me, that's the million-dollar question: if we're so right about what people in this country want, why is the left so weak?"

But he persists. A father of two, he brings up a deathbed quote attributed to Dr. Seuss: " `We can do better.' I feel like, if people organize, they'll do better: that's the promise of democracy."

His five-year-old party has doubled its enrollment to 100,000 — around 2 percent of the vote in New York State — and has its own line on the ballot in 530 races this fall. Historically, it has union ties and a tendency to endorse Democrats: 850 of them in 900 races over four years. The list includes Senator Hillary Rodham Clinton, who picked up 103,000 votes on the Working Families line — "We needed her more than she needed us" — and Representative Timothy Bishop, a congressman from Suffolk County whose victory margin over a Republican incumbent was nearly identical to his Working Families votes.

A previous attempt at starting a third party with a similar agenda and a national profile, the New Party, fizzled in 1997 after the Supreme Court denied it the right to cross-endorse in all 50 states. Working Families is state-bound; still, Mr. Cantor is jazzed that most of the Democratic candidates for president keep in touch. "Third-party politics in America can be a fool's errand unless you do it the way we're doing it," he says, banging the wobbly square of wood that serves as his conference table. "This is not about protest. This is not some 18-month march to freedom. This is the work of a lifetime. He said zealously."

Mr. Cantor, the sharpie, has already figured out that the surest way to prevent a guest from poking fun at his earnestness is to do it himself. (He mentions, with a disarming grin, that for him, idealism is a more useful commodity than cynicism.) Touchι: the high ground goes to the guy who reads Primo Levi and confines spats with his wife to whether television or the automobile is mankind's most divisive invention. He sheepishly confesses to car ownership and patronage of "Law and Order": one of the show's actresses lives on his Park Slope block.

So he does fall off the wagon and, in non-organizational moments, enjoy mainstream TV even if his wife, Laura Markham, a psychologist, gives him grief for it? Sure he does. And he returns the grief. After they married, he says he told her this: "I finally get to sleep with my shrink." Hey, that's a joke; nobody's a political zealot 24/7. Not in this party.