BOSTON -- I am not ordinarily a superstitious type, but I'm willing to bet that 13 is going to be an unlucky number in the final political countdown. Cross your fingers and don't step on any cracks.

Last month, the president said no to the Family and Medical Leave Act. It was Veto No. 13. On July 25, Congress tried and failed again to override the president. It was Failure No. 13.

The family leave is not some radical or pricey piece of legislation. Even its chief supporter, Rep. Marge Roukema (R-N.J.) describes it woefully as ''a bill so minimal, it's almost an embarrassment to present it.''

It would give workers in companies of 50 or more employees the right to 12 weeks of unpaid, job-protected leave, with health benefits, to take care of a new baby, a seriously ill spouse or parent. That's all.

A lot of companies do better than that. A lot of states demand more than that. But a lot don't. Two years ago, even candidate Bush said that ''we ... need to assure that women don't have to worry about getting their jobs back after having a child.'' This year, Congress finally voted to place this floor beneath family life.

Then the president changed his mind, and Congress came up 54 votes short of an override. The numbers went bad. But if 13 turns out to be unlucky for some politicians, it's because family leave is more than a bill. It's become a measure of our values.

In a recent Wall Street Journal poll, pollsters Robert Teeter and Peter Hart drew a statistical ''story on social issues.'' They revealed a country ''that is not ideologically aligned with the left or the right, but that has a fundamental sense of what should constitute public morality in 1990.''

Their portrait of public morality includes family leave. A full 71 percent of Americans favor it, including more than half of the people who identify themselves as social conservatives.

Marge Roukema, who regards the Bush veto with the dismay of a fellow Republican, explains it this way: ''Family leave has become a defining issue. It's about kids. It's about grandma and grandpa. It's about health care. It's about the two-worker family and what it means to be middle class in America.''

To be middle class these days means being squeezed. Between work and family. Between bills. Squeezed by the clocks. Squeezed by what Barbara Ehrenreich describes as ''the fear of falling'' into poverty -- an anxiety more powerful than acrophobia.

This theme is likely to appear in more than one election campaign. The incumbent who voted against medical leave will have to explain why he opposes the right of a parent to take care of a baby or a dying mother without losing a job. He'll have to explain why American workers don't deserve the same rights as their competitors in Japan or Germany -- why we should share the precarious status of Third World workers.

For the most part, opponents of the bill claim to be in favor of leave but opposed to mandates. They say that mandates shackle the benefits of free enterprise. But now even business leaders have broken ranks.

On the unlucky day of the unsuccessful override vote, Lawrence Perlman, president and chief executive office of Control Data, wrote in The Post that the bill was a ''moderate and appropriate response to dramatic changes in the American work force.''

Over the years, Perlman said, the government has mandated a safe work place, a minimum wage, Social Security. ''Congressional mandates,'' he said, ''not only ensure fair treatment of workers but also nullify the advantage companies that do not treat their employees fairly would have over those who do.''

Not one piece of family legislation has yet come out of this Congress or this administration. There is a greater sense of urgency about a national bank crisis than about a national family crisis. For the most part, family problems are still defined as private, personal.

In that much-heralded speech at Wellesley College, the president's wife told the young graduates, ''Your success as a family, our success as a society, depends not on what happens in the White House but what happens inside your house.'' Not quite. Not always.

Success as a family, success as a society, can also depend on what happens inside the White House and inside Congress. For a working woman with a newborn child, a working man with a sick wife or mother, the message from Washington has been: Tough luck. But luck, like numbers, has a way of changing.