Democratic presidential candidate Hillary Clinton on Thursday offered new details about her plan to make sure all workers can take time off, with pay, in order to care for a newborn or sick relative.

In so doing, she drew two contrasts -- a small one with Democratic rival Bernie Sanders, who would finance his own paid leave proposal differently, and a big one with the Republican presidential candidates, who wouldn’t guarantee paid leave at all.

Under Clinton’s plan, any worker could take up to 12 weeks off from work to play the role of family caregiver or to recover from an injury or illness. During that time, the worker would be eligible to receive replacement wages, up to two-thirds of his or her salary. The Clinton campaign didn’t provide many details on the formula for calculating the wages, but noted that a worker would qualify only after completing a minimum number of hours in the previous year.

The proposal, if enacted, would patch a major gap in America’s safety net. Workers in every other developed country are entitled to paid leave, in some cases for more than a year. U.S. workers are only eligible for unpaid leave -- that is, they can take time off, but with no guarantee they will get wages during that time. And, by law, only workers in companies with at least 50 workers have that right.

Some companies provide paid leave anyway. In the last year, high-profile employers like Facebook and Goldman Sachs introduced or expanded paid leave for their employees. But the majority of American workers aren't eligible for paid leave, and the ones who need it most -- food servers, sales clerks, and other people who can’t afford to forgo paychecks -- are the least likely to have it.

Clinton's proposal closely resembles a bill that’s been circulating on Capitol Hill, sponsored by Sen. Kirsten Gillibrand (D-N.Y.) and Rep. Rosa DeLauro (D-Conn.). Sanders, the senator from Vermont who is Clinton’s chief competition for the Democratic nomination, is among its co-sponsors in the Senate and has been touting its virtues repeatedly, and enthusiastically, on the campaign trail.

But Clinton’s proposal differs from the bill in one crucial way. In order to finance the replacement wages that workers would get, the Gillibrand-DeLauro bill would impose a small payroll tax, of 0.4 percent, that employers and employees would split evenly. According to the National Partnership for Women and Families, that works out to about $1.50 per week per worker.

Sanders has said he supports that approach, because it would represent a tiny sum that the benefits would more than justify. Advocates of this approach note that Social Security and Medicare Part A have similar financing schemes -- and argue that this “social insurance” approach, in which all workers contribute a small amount through payroll taxes, gives programs political resiliency.

They also say it’s administratively simple, since an agency like the Social Security Administration already runs such programs and could take on paid leave with relative ease.

Clinton has criticized that approach repeatedly because it would mean higher taxes on lower- and middle-income workers. Instead, she has said, government should finance the new benefit by imposing new taxes on only the wealthiest Americans. Clinton says it’s a matter of fairness, since incomes for the wealthy have been rising quickly, but wages for the middle class have been stagnant.

Sanders will give a major speech about paid family leave on Friday, in Iowa, site of the first presidential caucus. It’s entirely possible -- some might even say likely -- that the Clinton campaign made its announcement in an effort to preempt him.

Paid leave policies lead to better outcomes for mothers, children, and families. Betsey Stevenson, University of Michigan economist

But the real significance of Clinton’s proposal is probably what it portends for the general election -- and beyond.

Sen. Marco Rubio (R-Fla.), the only Republican presidential candidate to address the issue formally, has said he’d offer small tax breaks to companies that offer paid leave -- an approach unlikely to have much impact, except perhaps to help well-off workers. On the whole, Republicans have said they oppose paid leave guarantees, arguing that such regulations and programs make it harder for businesses to operate and end up hurting the economy.

That proposition has had at least one real world test -- in California, which a decade ago implemented a paid leave program much like the one Democrats have in mind now. Researchers have found the program offers clear benefits, allowing more workers to take paid leave and contributing to better maternal and child health as a result. They have not found evidence of damage to the business climate.

“The benefit of being one of the last countries in the world to adopt paid maternity leave is that we have been able to learn from other countries' experiences and the results are clear,” Betsey Stevenson, a University of Michigan economist and former adviser to President Barack Obama, told the Huffington Post on Thursday. “Paid leave policies lead to better outcomes for mothers, children, and families.”

Republicans will likely control the House of Representatives, and maybe the Senate too, even if a Democrat wins the presidential election. That means both the Clinton and Sanders proposals would face stiff odds of passing. But the issue will probably figure into the fall campaign, and it may figure prominently.

To advocates like Heather Boushey, chief economist and executive director of the Washington Center for Equitable Growth, that’s a welcome sign that American politics is finally talking about the challenges of parents who also have jobs. “This is the first presidential election that we’ve had a national debate, at this level, about work-family policy,” said Boushey, who is also an outside adviser to the Clinton campaign. “That’s very exciting.”

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