Sens. Joni Ernst (R., Iowa) and Mike Lee (R., Utah) fired their opening volley Tuesday in what is likely to be a spirited congressional debate about implementing paid family leave (PFL) across the United States.

The pair introduced the Child Rearing and Development Leave Empowerment (CRADLE) Act, their proposal to create a federal policy that would partially replace lost income when a mother or father takes time off of work to care for a newborn or newly adopted child. As with other Republican proposals to implement PFL, the CRADLE Act would allow parents to draw on their Social Security entitlements early, replacing their income in exchange for a slightly delayed retirement further down the road.

"Millions of moms and dads in Iowa and across the country struggle with the realities of child birth and infant care while also working hard to put food on the table and raise strong and health families," Ernst said at a Tuesday morning press conference. "It's long overdue that Congress not just have a conversation on these matters, but get serious about a path forward."

The U.S. Department of Agriculture estimated in its most recent report that a newborn child would cost middle-income Americans more than $12,000 in the first year of his or her life alone. At the same time, newborns are labor-intensive, usually requiring one or both parents to take time off of work—in other words, forcing Americans to forgo steady income exactly when they need it most.

Since 1993, Americans have been federally entitled to three months of unpaid leave from work to care for a newborn child. But of 41 developed nations identified by the Pew Research Center, the United States remains the only one not to have mandatory paid leave for new parents. The Urban Institute estimates that just 14 percent of U.S. employees enjoy PFL as a benefit, with access far more likely to be available to highly educated and skilled mothers.

Four states and the District of Columbia have passed laws to provide PFL within their jurisdictions, but there is an increasing consensus on left and right that a broader, national policy is required. Lead by first daughter Ivanka Trump, a bevy of Republican policymakers—including Sens. Ernst, Lee, Marco Rubio (Fla.), and Bill Cassidy (La.)—have been working on proposals to implement paid leave in a budget-neutral way.

"Families, of course, are the bedrock of our society. The family is the fundamental unit of society, upon which the success of society is contingent," Lee said. "For that reason, I've made it a point in my service in the United States Senate to make sure that we get family policy right."

If implemented, the CRADLE Act would require expectant parents seeking to receive benefits to register with the Social Security Administration and their employers. Approved recipients would then be entitled to up to three months of paid leave, compensated at the same level they would be paid at when they retire at normal retirement age.

That amount declines as income increases (so that more benefits accrue to lower-income recipients). According to Ernst and Lee's offices, this means that an individual making $17,000 a year (the federal poverty line) would see about 74 percent of their monthly net income replaced; a person making approximately $50,000 a year would see about 50 percent replaced. This number could be added to state- or employer-provided paid leave, up to the total of the recipient's original income.

Parents who chose to take advantage of Social-Security-based PFL would "repay" their early withdrawal by postponing retirement by two months for every month they took off. Further, recipients would only be allowed to draw Social Security payments if they were actually taking time off—a distinction, Ernst said, from the Rubio proposal, which permits individuals to draw additional benefits while still working. The proposal is also designed to be "voluntary," meaning that childless individuals are not expected to pay for the time off of individuals with children.

Ernst emphasized in her remarks that the CRADLE Act was a "discussion draft," and that she and Lee were eager for further input from Congressional colleagues on both sides of the aisle. She did not explicitly say where the White House came down on the bill, but did note that she and her colleagues had been working with Ivanka in its crafting.

This tentative status makes it clear that the CRADLE Act is intended to be part of a longer conversation about the eventual shape of a possibly bipartisan PFL solution. Democrats have their own version, the FAMILY Act, which pays for three months of PFL with an expanded payroll tax. Haggling over how to pay for family leave is likely, in the coming months, to be one of the major barriers to the eventual passage of any final bill.