Washington — When she moved from Thailand to the U.S. as a teenager with her father and brother in 1984, Sen. Tammy Duckworth, D-Illinois, and her family faced financial hardship.

"We showed up in Hawaii with like $300 to our name," Duckworth told CBS News.

Because her father, Franklin Duckworth, who had served in the U.S. Army in World War II and the wars in Korea and Vietnam, struggled to find a job in America, Duckworth said her household was "essentially destitute" and relied on government food stamps to get by. Exacerbating their predicament was the absence of her mother, who remained in Thailand because she could not legally travel to the U.S. with her family, despite being the wife of an American veteran and mother of two U.S. citizens. Her father's work with refugees after his army service had taken them around the world, but the family had not lived in the U.S. before they moved to Hawaii.

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"If my family did not have access to food stamps, I would've dropped out of high school and I don't know where I would be today — but I would probably not be a United States senator," she said.

Duckworth's opposition to a proposed rule by the Trump administration that would prevent many low-income immigrants who use public benefits from obtaining U.S. residency is deeply rooted in her personal experience as an adolescent. The one-term senator said she can't imagine how her father could've chosen between accepting food stamps to feed her and her brother or bringing his wife and the mother of his children to America.

"That's not a choice we should be forcing families to make," she said.

What it means to be a public charge

The "public charge" term is used by U.S. Citizenship and Immigration Services (USCIS) to describe a person whom the government believes will rely on government welfare programs for subsistence. People who fall into this category are deemed inadmissible to the U.S. "on public charge grounds."

The Trump administration is now considering a rule change that would significantly expand the definition of a "public charge" and would make it more difficult for certain low-income immigrants to secure permanent residency or temporary visas.

The "public charge" standard was first codified into U.S. immigration law in 1882 and again in the Immigration and Nationality Act of 1952, which stipulated that those who were deemed a "public charge" would be subject to deportation or barred from entering the country.

Immigration authorities currently ask green card applicants to prove they won't be a burden on the country, but the new regulation would require caseworkers to consider the use of government housing, food and medical assistance — like the popular Section 8 housing vouchers, the Supplemental Nutrition Assistance Program (SNAP), as well as Medicaid and Medicare's Part D prescription drug coverage — by immigrants seeking to reside in the U.S. on a permanent basis.

The complex, more than 400-page proposal would subject households who fall below certain income thresholds, based on the number of family members, to the "public charge" test, which would also consider how well applicants speak, read and write English. Asylum seekers and refugees would be exempt from the test.

Since it was unveiled by the Department of Homeland Security in September, the proposed rule has provoked scathing criticism from Democrats, immigrant advocates and medical groups, who believe the regulation change will harm low-income immigrant communities — particularly children. When the 60-day public comment window on the proposed rule closed on Dec. 10, 216,097 comments had been submitted.

Regulation could jeopardize "the health of millions of children," says pediatrics group

The American Academy of Pediatrics is one of many medical advocacy groups which have been outspoken in opposing the proposed rule change. Julie Linton, co-chair of the academy's interest group on immigrant health, said the proposal has already been having a "chilling effect" on immigrant communities since a draft was leaked in 2017, prompting fearful immigrant parents to forego "bread and butter" government benefits which they and their children, often U.S. citizens, qualify for.

"This is such a confusing regulation, and we're in such a time of fear and uncertainty for immigrant families — and families of color in this country and families living in poverty right now — that this is really jeopardizing the health of millions of children, well beyond those that would definitely be impacted by it," Linton told CBS News.

As a practicing pediatrician in South Carolina, Linton said she has seen the effects of the proposed rule on some of the immigrant families who visit her clinic. In one occasion, Linton said she asked a single mother if her daughter was enrolled in WIC — a federal food assistance program for low-income pregnant and breastfeeding women and children under the age of five — after determining that the child did not have sufficient access to nutritious food. Linton said the immigrant mother told her she believed she could be deported if she enrolled in the program, even if her child was a U.S. citizen.

"It puts me in an incredibly difficult position to do what I know keeps people healthy, which is recommend enrollment in services, and also have this underlying understanding that for many of the families I serve, they're being placed in a trap: do we accept the services that keep us healthy and our children healthy? Or do we risk being able to stay together?" she said.

A recent study by the Urban Institute's Health Policy Center predicts that as many as 6.8 million U.S. citizen children enrolled in Medicaid and the Children's Health Insurance Program (CHIP) with parents who are non-citizens could be affected by the new regulation.

Although the proposal does not include Medicaid and CHIP assistance in its "public charge" considerations, researchers at the Health Policy Center believe immigrant parents, particularly in Latino and Asian American communities, will drop these benefits due to concerns surrounding their immigration status and ability to remain in the U.S. legally with their children.

Democratic senators say rule will also hurt military green card holders and elderly immigrants

Duckworth — who followed in her father's footsteps and served as an Army pilot during the war in Iraq, where she suffered severe combat wounds — said the Defense Commissary Agency, an arm of the Department of Defense which provides discounted groceries and household goods to active-duty, reserve and retired members of all uniformed services in the U.S. and their families, could also be affected by the rule change.

"A large percentage of the military's grocery store, the commissary receipts, come from food stamp recipients," she said. "So, there are military men and women who are green card holders who also receive food stamps — and their families do."

Servicemen and women with permanent residency — who can enlist in the military as long as they live in the U.S. and speak, write and read English fluently — are eligible for benefits offered by the Defense Commissary Agency. And according to its website, the agency accepts food stamps and other forms of government assistance as methods of payment. The proposed rule by the administration, however, would theoretically not affect green card holders.

Sen. Maize Hirono, D-Hawaii, said she believes elderly immigrants with limited English-speaking skills will also be targeted by the rule. The proposal states that English-language proficiency is "relevant in determining whether an alien is likely to become a public charge in the future." The regulation also stipulates that a diagnosed medical condition which requires extensive medical treatment will "weigh heavily" in the government's determination of whether an immigrant is likely to become a "public charge."

"My grandparents were legal permanent residents, they attained that status. But they never really learned how to speak English," Hirono told CBS News. "But they were very much a part of my immigrant family's ability to keep a roof over our heads and food on the table."

Hirono, the Senate's only immigrant, was born in Japan and moved to Hawaii when she was nearly eight years old with her brothers and mother, who was fleeing an abusive marriage.

The dean of Hawaii's congressional delegation added that she would be surprised if the administration modifies or scraps the proposal based on the tens of thousands of public comments submitted by the public.

"This is part of this administration's policy, their anti-immigrant agenda and it is very harmful to thousands and thousands — I would say millions — of families who are already here who will be impacted negatively by this rule," Hirono said. "But does this administration care? No. In fact, that is exactly what they want to visit upon all these families."

DHS secretary says new regulation promotes "immigrant self-sufficiency"

In a statement to CBS News, Department of Homeland Security Secretary Kirstjen Nielsen said "long-standing" federal law requires immigrants seeking to come to America to demonstrate they can support themselves financially.

"This proposed rule will implement a law passed by Congress intended to promote immigrant self-sufficiency and protect finite resources by ensuring that they are not likely to become burdens on American taxpayers," she added.

Nielsen said her agency is "welcoming" of the public comments submitted on the new regulation.

USCIS spokesperson Michael Bars told CBS News that his department will give the more than 215,000 comments on the proposed change "due consideration" and address them in a final rule next year.

"While we cannot respond directly to such comments at this time, much of the media reporting on the rule appears to reflect a fundamental misunderstanding of the Department's proposal," Bars added in a statement.

The department did not provide a timeline on the comment review process.

House Democrats vow to challenge proposal

If the rule is implemented, several House Democrats, who are poised to seize control of the chamber in January, pledged to challenge it with their majority.

"We will look to reverse it. We'll look to introduce legislation that will then reverse that rule change," Rep. Adriano Espaillat, D-New York, told CBS News. "I'm sure that is one issue that will be part of the broad gimmick of immigration-related issues that will be taken up next year."

Espaillat, who represents predominantly working-class immigrant neighborhoods in New York City, said the proposal runs "contrary to the tradition of our nation" by placing immigrants in a position "where they have to determine between SNAP, food stamps or housing vouchers, and their immigration status."

"That's the tragic narrative of this issue," he added.

Democratic Rep. Lou Correa of California, the state with the largest foreign-born population in the U.S., said his party will use all "powers available" to challenge the proposal and "make sure that these kinds of rules are not implemented."

The Orange County lawmaker linked the proposed rule to the $867 billion farm bill passed by Congress earlier this month. "That subsidizes American farmers. That's good to keep American farmers strong economically," he said. "And one way to subsidize those farmers is with food stamps. We buy their products. And it's good to give them to hungry people — irrespective of immigrant status. It's good public policy. It's a Christian thing to do."

Correa added that the new regulation neglect's America's long history of accepting poor and working-class immigrants from all corners of the globe.

"We come here not because we are wealthy from our country that we leave, but because we're looking for freedom, we're looking for economic opportunity. That is why people come to America." he said. "The king of England did not come to America."