And this belief is perfectly respectable as far as it goes. The problem is that we, as a nation, have been running this experiment for decades now, and the verdict is clear: Without government assistance — or nudging — most businesses will never feel the obligation to pay for family leave on their own. According to the Bureau of Labor Statistics, only 11 percent of private-sector workers got paid family leave in 2012. As Mr. Obama noted this summer, “many women can’t even get a paid day off to give birth.”

Ms. Fischer has attempted to provide a bipartisan solution to this problem by co-authoring a bill with Angus King, a Maine Independent who caucuses with Democrats, that would provide tax credits to businesses offering families paid leave. This notion is surely more palatable to the Republican-led Congress than Mr. Obama’s initiative, which involves $2.2 billion in spending. But Ms. Fischer frankly concedes that she doesn’t expect Congress to entertain their bill this session.

Yet there’s a solid case to be made that paid family leave is good for business. Three years ago, Rutgers’ Center for Women and Work issued a report showing that women who took paid leave were far more likely to be working for the same employer a year later. It also added that women and men who returned to work after paid leave were far less likely to collect food stamps or public assistance in the year following their child’s birth. As Ms. Fischer herself says, family leave also helps people on her staff “do their job well. They’re not preoccupied, they’re not worrying about everything that’s happening at home when they’re at work.”

IT’S already a cliché to point out that the United States is the sole industrialized nation without a paid maternity leave policy. (In case you’re wondering what we have in common with Papua New Guinea, this is it.) According to a Pew study last April, our inability to provide affordable child care as a nation may help explain our declining rates in women’s participation in the work force.

Absent state funding and intervention on this matter, it falls to individual families — small, fragile, closed little loops of two parents (if that) — to resolve what the state and the private sector do not. It’s utterly exhausting to them. It means a scarcity economy at home, with spouses quarreling about whose career is more important and whose time is more valuable. Someone almost inevitably needs to scale back ambitions or earning power in order to make life work.

And that someone, usually, is the mom. Which brings me to this final plea: Even the most enlightened Senate offices — and private-sector offices — seem to believe that fathers require fewer weeks of leave than mothers. Mr. Obama himself referred to “maternity leave” in his State of the Union address, not “parental leave,” as he had in previous statements. There are hundreds of arguments to make in favor of parity between the sexes when it comes to family leave. (High among them: More engaged dads allow their wives to lean in; more and more gay men are having kids, and shouldn’t be subjected to different rules.) But here, I’m going to name a very modest reason: It would make things more tranquil at home. Over and over again in my research, I hear mothers of newborns say, “When my husband comes home from work, he wants to comfort the baby, but he can’t, because the baby is used to me.” And then the fights begin. Because Mom is tired. Mom wants a break.

I doubt mothers would be hearing such things if fathers took equal time off from the get-go — paid or unpaid. Couples would be dividing child care and the domestic tasks more equitably (at present, mothers do nearly twice as much of both); they would also have two expert hands on deck. Their marriages would be stronger. And they’d have the Republican Congress to thank.