The U.S. House of Representatives rarely behaves in a unanimous way — even the declaration of war against Japan in 1941 had a lone dissenter — so when it does march in lockstep, something is afoot.

Such as the 409-0 vote the other day supporting a resolution that “applauds” moms (dads, too) who stay at home with the kids instead of going off to work.

But what looked on the surface like a harmless endorsement of the warm and fuzzy in life goes much deeper, down to the core of the Republican agenda: tax equity for the “traditional” family, starting with a tax credit for families in which one parent forsakes career for parenting.

Since 1976, working parents have had the Dependent Care Tax Credit to defray child-care costs and stay-at-home parents have grumbled “what about us?” for nearly as long. Now, it’s gone beyond grumbling to a social movement lawmakers will have a hard time resisting. It is at the core of the upcoming child-care debate.

Conservative backers of a tax credit for stay-at-homes say the current setup of rewarding parents for having someone else raise their children amounts to social engineering, with the socialistic government indoctrinating the pupae while the drones work. At the other fringe, liberal opponents say it’s all a right-wing ploy to gut any federal support for day care and to keep those uppity women out of the workforce.

The truth, of course, lies somewhere in the middle. This isn’t Donna Reed vs. Brave New World. Many couples do make a considerable sacrifice, in both income and career advancement, so one can stay home during the pre-school years. Many couples simply don’t have the option — that second income isn’t buying a vacation in Grand Cayman, it’s buying groceries.

Which is why the middle ground is so important here. President Clinton’s new $21.7 billion child-care initiative proposes to expand the child-care tax credit, to give businesses tax breaks for offering care, to increase subsidies for low-income parents, but it makes no mention of the stay-at-homes.

A counter-proposal, sponsored by a group of senators including Maine’s Olympia Snowe and Susan Collins does. It reduces or eliminates the tax credit for high-income families and it extends the credit to stay-at-homes for a maximum of $900 a year. That certainly does not compensate for a lost paycheck, but it might offset a few expenses during those early years and it might send a message to those who do tighten their belts that the effort has not gone unnoticed.

Of course, some critics have noted the irony — the same conservative Republicans who last year told welfare moms to get a job and put the kid in day care now are ready to pay middle-class moms to stay home. Other critics suggest that those who would reshape society in the image of their desire might start out by seeing that the paycheck brought home by today’s Sean Telemarketer has the same buying power as that of yesteryear’s Joe Steelmill. Then mom — or dad — could stay home.