Congressional Democrats this week are set to take their first steps toward adopting a $450 billion plan that could improve child care nationwide, marking an early attempt to lock in a major element of President Biden’s economic agenda at a moment when it is in political peril.

The new spending could amount to the largest-ever investment in federally backed child-care programs, with Biden and other Democrats laboring to ease the financial burdens on parents, offer higher wages to caregivers and ensure all children ages 3 and 4 can enroll in free prekindergarten.

But the funds are part of a fluid, still forming $3.5 trillion package that has become the subject of considerable sniping even among Democratic lawmakers in recent days. Democrats envision a broad reimagining of federal health-care, education, immigration and tax laws, even as liberal and moderate lawmakers quarrel over the price tag and scope of their policy ambitions.

Amid the squabbling, Democrats have stressed that the new child-care investments are urgent. They say the proposed spending compensates for decades of neglect compounded in severity during the coronavirus pandemic, which forced many child-care centers to shutter — all the while leaving working parents with few options.

“The average family cannot afford child care, and without child care, you cannot go to work,” said Rep. Robert C. “Bobby” Scott (D-Va.), chairman of the House Education and Labor Committee and one of the architects of the plan.

Scott’s panel is set Thursday to take the first step toward securing those funds. Entering the debate, some liberal-leaning Democratic lawmakers have pushed for more spending — and more-expansive benefits — than moderate members of their party may be willing to support. The potential political fault lines echo those that have troubled the broader $3.5 trillion package in recent days.

Adding to the challenge, some of the newly proposed child-care subsidies may provide only limited relief to families at a time when the country is already struggling to recruit and retain caregivers during the pandemic. The House plans to phase in some of its benefits over the next six years, a timeline that lawmakers described as a reflection of the significant work ahead to correct years of policy inaction.

“All of us would love to say you can start this tomorrow,” said Sen. Patty Murray (D-Wash.), the co-author of a precursor to the child-care proposal in the package.

“But the fact is, we have not done this in our country before,” added Murray, the leader of the Senate Health, Education, Labor and Pensions Committee. “And it is going to take some time to build it and get it right.”

Democrats have eyed improvements to the country’s child-care programs for decades, citing persistent economic gaps that have disproportionately burdened low-income families. The federal government annually spends more than $8 billion on helping parents obtain access to preschool and other services. Yet eligibility rules in some cases are narrow, the benefits are not robust and state funding has flagged over time, severely limiting the subsidies and the number of Americans who can obtain them. Only about 1 in 6 children eligible for child-care assistance receive it, according to an analysis from the Center on Budget and Policy Priorities before the pandemic.

“If we were to imagine that applied to fifth grade or eighth grade, we’d be horrified by the state of what’s available to children and families,” said Laura Dallas McSorley, senior director of early-childhood policy at the left-leaning Center for American Progress.

The gaps have widened in the aftermath of the coronavirus, which has unleashed unprecedented hardship on the child-care industry and those it seeks to serve. Already struggling to pay the bills, some Americans have found added headaches in obtaining child care because of closures and capacity restrictions, forcing many parents to make the difficult choice between caring for their children or keeping their jobs. The toll has been greatest on women, who have left the workforce in droves, prompting some experts to describe the current conundrum as a “she-cession.”

Seeking to stem the tide, Democrats in Congress have approved about $50 billion to aid child-care centers since the earliest days of the pandemic, hoping the stimulus aid might ensure these cash-starved institutions can stay afloat. The money has helped, experts say, but it also has injected fresh urgency into long-running efforts to rethink the entire system.

Earlier this spring, Biden recommended a total of $450 billion for early child care, including funds to provide free prekindergarten. Since then, Democrats have worked to adopt Biden’s proposal as part of the broader tax-and-spending measure they plan to move through a process known as reconciliation, which will allow the party to sidestep a Republican filibuster.

The process has opened the door for Scott and other lawmakers in the House, along with Murray and her peers in the Senate, to advance a version of the legislation they introduced in April to invest significant new sums in child care. The work begins Thursday, when the House panel led by Scott is slated to begin debating and voting on a modified version of the $450 billion plan.

Under the proposal, Democrats would devote some the new spending toward helping every child ages 3 and 4 obtain two years of universal prekindergarten, with additional sums set aside for expanding other child-care access and affordability. Much of it is stems from a state-focused block grant program that helps subsidize parents’ access to services including day care.

The new benefits for families would be parceled out on a sliding scale, with those making below 75 percent of a state’s median income receiving new subsidies that cover the costs of child care for children under age 5. At the top, families who earn up to 200 percent of their state’s income average would have their costs capped at 7 percent. Democrats have proposed phasing in the support over six years, meaning families who earn more may have to wait longer to see the effects of the bill.

“Tens of millions of people will be newly eligible for vouchers,” Scott predicted in an interview this week.

In addition to the financial aid, Democrats also seek to upgrade child-care facilities and put in place new programs to help train caregivers, aiming to address shortages that leave parents with few options for care. And Scott and Murray also have proposed billions of dollars to help states cover the cost of raising child-care workers’ pay, since many of them earn less than $12 an hour — putting them below poverty-level wages.

The investments seek to address some of the immense disruptions to child-care centers that continue to hamstring their operations and paychecks that continue a year later. The National Association for the Education of Young Children found in July that 4 in 5 workers at child-care centers throughout the country reported their facilities were understaffed, and more than 1 in 3 caregivers said they were considering leaving their job partly as a result of poor pay.

The ideas have broad support among Democrats, though some in the party had sought to widen the plan even further. Liberal lawmakers in the Congressional Progressive Caucus, for example, pursued more-universal child-care coverage with no caps on spending. They said the changes could benefit Americans who live in high-cost cities, where their income on paper looks higher than it is in practice, leaving them to suffer the same child-care troubles as their peers elsewhere.

“If you use a standard of 150 percent of state median income to determine benefits, you are actually going to penalize the states and localities that have passed a $15 minimum wage and are housing poor,” Rep. Pramila Jayapal (D-Wash.), the leader of the caucus, said in an interview last week about an earlier version of the bill. She pointed to Seattle in her political backyard, noting her calculations reflected that the bill might “leave out most of the middle-class families in my district.”

But Democrats who chiefly authored the bill say they believe it strikes the right balance. And they expressed uncertainty about the prospect for changes given the broader political realities facing the entire reconciliation package, which is capped at $3.5 trillion — and is likely to be lower as a result of moderate party lawmakers who see the price tag as too high.

“We have to keep it under a certain cost,” Scott said. “You are limited by the top line.”

Democrats also face the added challenge of distributing the aid expediently, seeking to remedy the current woes of the pandemic while addressing the broader needs of the child-care system. Only those who are currently eligible for child-care funding under existing federal programs may be eligible to receive it at first, meaning millions of Americans may have to wait up to five years to take full advantage of the reconciliation package.

Asked about the delays, Scott pointed to a problem with “capacity,” citing the fact it takes time to train new workers and build or improve facilities that can handle a potential influx of children.

“There was a child-care problem before the pandemic,” he said.