THE EQUAL RIGHTS Amendment's narrow defeat in the Florida Senate last week was a disappointment, but hardly a fatal one. ERA is steadily picking up strength; it's just that some of the Florida senators are a bit slow in reading the message. The amendment has to be ratified by three more states before the deadline in March 1979. Within those two years, it's rather likely that a couple of the legislatures that earlier rejected it will change their minds. There are also a couple of legislatures that have never quite summoned up the courage for a full vote on it, and perhaps one of them - Virgina's - will be helped by the next election to see the error of its retrograde ways.

In the Florida debate, there was the usual frivolous talk about unisex bathrooms. But the real question is whether women need special insulation and protection and must pay for this with special legal disqualifications, simply because they are women. One senator, voting against the amendment, observed that most members of the opposition were housewives who depended on their husbands for their families' incomes. Most of the supporters, he added, seemed to have jobs of their own.

As broad generalizations go, that's not a bad one. While ERA gets a lot of help from women who have never worked outside the home, it's the remarkable increase in the number of women with jobs, who are economically independent, that gives the movement its special force. A generation ago, in 1950, just about a third of all American women were in the labor force. By 1970, it was 43 per cent. Last year it was up to 47 per cent and still rising fast.

Political messages are delivered most effectively at the polls. In the Virginia elections this year, we suspect that a couple of interesting things are going to happen. It's very likely that the number of women elected to the legislature is going to rise sharply. It's also possible that some of the statewide candidates will discover ERA to be an issue with more power behind it than they had realized. And Virginia isn't the only state that votes before 1979.

The debate over the amendment has always been conducted at two utterly separate levels. The supporters always want to talk about the effect of constitutional language on specific legal situations. The opponents usually want to talk about social change and its threats to a certain kind of traditional family life. The crucial voted here aren't the ones cast last week in the Florida Senate, but the ones cast every day by women entering the job market, going into the professions and running for public office. Because these numbers rise every year, ERA's chances - despite its occassional setbacks - look somewhat better than the outcome in Florida would seem to suggest.