WASHINGTON - Sen. Kirsten Gillibrand long has called on Congress to provide paid family and medical leave to the millions of Americans who don't have it. So when she found out last week the plan had been dropped from her party's landmark spending bill, she began an 11th-hour campaign to try to resurrect it.

The New York Democrat targeted the chief objector to the program, Sen. Joe Manchin III, D-W.Va. She hit the phones Friday and fired off a flurry of texts to her moderate-leaning colleague that continued into the weekend, saying she would be even willing to "meet him in D.C. or anywhere in the country" to make the case for the benefits, she said in an interview.

Yet Manchin refused to relent, Gillibrand said, resisting her latest entreaties much as he had the many alternatives that Democrats had presented to him in recent weeks.

Still, Gillibrand remained undeterred. "It's not over until it's over," she said.

The burst of activity from Gillibrand reflected what some reluctantly have acknowledged is a last gasp attempt to salvage one of their most popular policy promises. With the House set to vote on a sweeping spending measure as soon as Tuesday, it marked a new test as to whether Democrats, largely led by women in the House and Senate, could sway Manchin and deliver the help they long have promised to millions of Americans.

The paid-leave plan that Democrats originally envisioned would have provided 12 weeks of aid for Americans who fall ill, need to care for a sick loved one or are tending to the birth of a new child. Tens of millions of workers don't have access to some or all of these benefits now through their employers, according to federal estimates, resulting in a gap that has hit low-income families and women the hardest.

Lawmakers tucked the expansive proposal into the original $3.5 trillion economic package they unveiled earlier this year, a broader overhaul of federal healthcare, education, immigration, climate and tax laws. But it soon became a casualty of the tense negotiations between Congress and the White House. It surfaced less frequently in some of Biden's public remarks - and eventually fell out of his spending blueprint - as top aides whittled down their ambitions to win over the likes of Manchin.

Democrats, including Gillibrand, still stress the resulting $1.75 trillion deal is historic in its own right. But its omission of paid leave nonetheless has left many party lawmakers spoiling for a new fight. At a press conference Thursday, House Speaker Nancy Pelosi, D-Calif., pledged to reporters she would keep fighting "for the babies."

A day earlier, an incensed Sen. Patty Murray, D-Wash., hammered Manchin indirectly, stressing that Democrats are "not going to let one man tell all the women in this country that they can't have paid leave." And a wide array of lawmakers including Sen. Kyrsten Sinema, D-Ariz., have placed calls to Manchin directly about the issue, according to a person familiar with the matter who spoke on condition of anonymity to describe private conversations.

"I do believe this is a unique moment in time," said Gillibrand, who spoke by phone late Friday, as she acknowledged that time is running out. "If I can get more time with him I'm optimistic I can find the right form."

Manchin declined comment.

The last-minute push on paid leave arrives as congressional leaders are racing toward a series of key votes on the president's fuller economic agenda next week. Little time remains to rethink the delicate $1.75 trillion plan that Biden forged in an attempt to unite warring centrists and liberals in his own party, resolving a months-long logjam.

The still-unfinished bill amounts to one of the largest investments in the federal safety net in history. It aims to help parents pay for childcare programs, establish universal, free prekindergarten for young kids and extend tax credits that have allowed millions of families to collect monthly checks.

Initially, Biden also hoped to include an expansive, 12-week program for paid family and medical leave as part of the package. He first proposed it as part of the American Families Plan he unveiled in the spring, building off a commitment he made on the 2020 campaign trail to ensure millions of Americans could take time off without risk of losing their jobs or paychecks - especially during the coronavirus pandemic.

"No one should have to choose between a job and paycheck or taking care of themselves and a loved one - a parent, spouse, or child," the president said in a speech to Congress this spring.

By summer, lawmakers had set out to turn those ideas into actual legislation, culminating in a nearly $500 billion House proposal to provide 12 weeks of leave with benefits scaled by income. The architect of that plan, Rep. Richard Neal, D-Mass., aimed to fund the program in the same way they hoped to cover the rest of the bill, using tax rate increases targeting wealthy Americans and profitable corporations.

"I felt pretty strong it was one of the most popular items in the package," Neal said in a recent interview

Yet House Democrats' foray immediately encountered trouble. Manchin and Sinema each had demanded massive cuts to the overarching $3.5 trillion price tag. Even though paid leave programs had been popular among lawmakers in the party - and some, including Sinema, had unveiled related legislation in the past - the centrist duo generally believed the total package cost too much.

Manchin, meanwhile, privately expressed to Democratic lawmakers, White House officials and paid-leave advocates a series of evolving concerns specifically with the proposed benefit program, according to five people familiar with his thinking, who requested anonymity to describe private negotiations.

At times, the West Virginia senator felt that a paid leave program could invite fraud, likening it to those who tried to collect unemployment even when they were not eligible. In some conversations with lawmakers and advocates, he asked about work requirements, even though employment is a condition for one to take leave in the first place, some of the sources said.

In other instances, Manchin raised the potential impact on small businesses, who needed workers to remain on the job. And in public and private, Manchin highlighted issues with the "solvency" of a new social benefit program, pointing to his long-documented concerns that existing federal entitlements, including Medicare, are running out of funds.

"I'm talking to everybody, but I've been very clear. To expand social programs when you have trust funds that aren't solvent, that are going insolvent - I can't explain that, it doesn't make sense to me," Manchin said last week, adding lawmakers need to "start paying for things."

Manchin's opposition put the White House in a bind. The paid-leave program, once a fixture in Biden's speeches, appeared to advocates to come up less frequently in his public comments starting in the summer. The change in tone troubled supporters for the program, some of whom said they were told privately by the White House for months they had nothing to fear - and should instead focus their attention toward shoring up support from Manchin.

By mid October, though, the White House informed Democrats they had to scale back the paid leave program, which opened the door for lawmakers to consider only a temporary, four-week benefit. The cuts left some in the party upset and advocates seething, though many accepted it as better than nothing.

Then, days later, the White House shelved the proposal entirely as part of the $1.75 trillion compromise that the president presented to Democrats during a closed-door meeting on Capitol Hill last week.

"It's outrageous, it's shameful," said Dawn Huckelbridge, the director of Paid Leave for All, an advocacy group. "Our view is very clear, a budget deal that doesn't include paid leave fails working families and it will not do what this package intends to do, which is build back better."

The White House did not respond to a request for comment. Karine Jean-Pierre, the principal press secretary, told reporters last week paid leave remains "a big priority" for the president, adding of the debate: "It doesn't end here."

The omission immediately touched off a frenetic new lobbying effort on Capitol Hill. The dissent last week even spilled out onto the Senate floor, where Murray joined other women in cornering Manchin as the news broke to press him on paid leave.

In an interview, Murray said on Saturday she and other women sought to explain to Manchin "what every woman and a lot of men in this country understand, which is when you just had a baby, [when] you have a seriously ill family member, it is an economic issue for [workers] that they be able to have that time."

Manchin in response told Democrats in that conversation he is not a "hard no," Murray said. But the entire fiasco still troubled Murray, who fretted that they had already made substantial cuts - and found it unacceptable to eliminate the program because "one man said he didn't want it."

Publicly, some of the new political pressure campaign came from women who knew first hand the importance of the paid leave program that Manchin opposed. Rep. Rosa DeLauro, D-Conn., who as a staffer in the 1980s took time away from her job to recover from cancer, expressed deep concern that Congress found itself unable to provide the same aid Americans that they have made available to federal employees.

"Why is it good enough for us and not good enough for everyone else in the country? We're the only industrialized nation that does not offer paid family and medical leave," DeLauro said in an interview this week, pledging to keep pushing for the program.

Pelosi, the mother of five, echoed the need to assist parents and promised to keep fighting for it at a press conference last week. Privately, she personally called Manchin to push to revive the program in recent days, according to a person familiar with the matter, who requested anonymity to describe the speaker's conversations. The speaker's office declined comment on the call.

So did Sinema, a former social worker, according to another person. The source said Sinema voiced her support for paid leave and discussed with Manchin potential ways to pay for it. Manchin in the past seemed receptive to a proposal that could use payroll taxes to fund leave benefits, three sources said. But the idea has presented political challenges, since Biden has vowed not to raise taxes on Americans making under $400,000.

Sinema's office declined comment for this story.

Gillibrand, meanwhile, ratcheted up her own personal advocacy campaign.

Behind the scenes, she and Manchin have discussed a wide array of ideas - including limits on paid leave benefits that might have only provided the aid to new parents. In a later interview, Gillibrand acknowledged the approach as imperfect, given the fact it threatened to leave out a majority of Americans who take leave as a result of an illness experienced by themselves or a loved one. But she said it felt it presented an option that might have opened the door for more legislating down the road.

Nevertheless, Manchin rejected the idea, Gillibrand recalled. She also presented data to him showing that 12 weeks of aid are critical for new, nursing mothers, who cannot obtain childcare before that point, and stressed it would help reduce the financial strain on federal healthcare programs by promoting wellness - and still, she said, Manchin didn't budge.

"He wants to [work on it] later," Gillibrand said, adding that some of the senator's objections stemmed from the vehicle by which Democrats hope to secure the new spending. "I think he has a mis-impression that this can be done easily with Republican support."