Ramesh Suman, a real estate agent in Antioch, Calif., remembers the client who refused to see a house after saying that it looked like it belonged to members of the Dalit community, a historically oppressed group of people relegated below even the lowest rung of the caste system once used in South Asia.

Bhim Narayan Bishwakarma recalled how a landlord accepted his deposit but later reneged on a rental after learning his surname, which is common among Nepalese Dalit families.

And Dr. Promila Dhanuka said that once word got around more than 15 years ago in Redding, Calif., that she had Dalit roots, some Indian American doctors stopped referring patients to her oncology practice.

While many South Asian immigrants face discrimination in the United States, those with Dalit ancestry — once deemed to be “untouchable” from birth — say they must also overcome being ostracized by fellow South Asian immigrants who cling to a social stratification that dates back millenniums. That has occurred even though untouchability and caste-based discrimination have been outlawed in India and Nepal for decades.

Nowhere in the United States has the subject been as prominent — or as divisive — as in California. Three years ago, the state’s Civil Rights Department accused two engineers of caste discrimination at Cisco Systems in a landmark lawsuit. This week, the State Legislature sent a bill to Gov. Gavin Newsom that could make California the first state to expressly prohibit such bias.

In more than a dozen interviews, people who identify as Dalits described various encounters with caste-based bigotry in the United States, in the form of wage theft, housing discrimination, mistreatment in the workplace and social exclusion.

They spoke of the shame and anger they felt hearing slurs used in reference to Dalits. Many said that they felt pressure to hide their identity and that they lived in constant fear of being “outed,” despite being in a country they saw as a haven free of the caste vestiges of their homelands.

“I really thought I had left untouchability or caste-based discrimination back in Nepal,” said Mr. Bishwakarma, who works at a convenience store in El Cerrito, Calif. “I never thought that one day I would be discriminated against just on the basis of caste in a country like the U.S.”

The issue has prompted fierce debate over how pervasive caste discrimination is within the South Asian community in America, which has grown dramatically in recent years and reached around 5.4 million people. Those who oppose an express ban say they believe such discrimination is rare and that writing it into state law will unfairly malign South Asian Americans by associating them with antiquated social beliefs.

In California, many community members have faced off against one another at the State Capitol and various City Council chambers, showing how immigrant communities can become factionalized as they expand and become more diverse.

Since 1965, most South Asians who have immigrated to the United States have been highly educated people who could trace their origins to the upper caste, in part because they had greater access to the resources necessary to qualify for skilled worker visas.

But the makeup of South Asian immigrants has changed in recent years, particularly among those from India, where affirmative action has enabled more people from oppressed communities to attend universities and move abroad.

While conditions generally have improved in South Asia for those who were once relegated to the lowest tiers, segregation based on caste remains persistent, and many people of Dalit background still face discrimination, mistreatment and violence.

Most Americans are unaware of the caste distinctions in South Asia, and the Cisco lawsuit served as a wake-up call to Democratic lawmakers in California. The issue is especially acute in the tech industry, where South Asians comprise a significant share of Silicon Valley workers, many of them first-generation immigrants.

“The more diverse California becomes, the more diverse our laws have to be and the further we have to go to protect more people,” Aisha Wahab, a Democratic state senator who introduced the caste discrimination bill, said in an interview. Senator Wahab is the first Afghan American elected to the State Legislature and the first Muslim to serve in the State Senate.

Opposition to the bill has been driven by some Hindu residents and organizations, who have been vocal throughout the year. They argue that the proposal unfairly targets Hindus because the caste system is most commonly associated with Hinduism.

They also say that existing laws prohibiting discrimination on the basis of religion and ancestry are sufficient, while pointing out that caste was outlawed in India more than 70 years ago.

“I personally see this as something that does not exist in society,” said Praveen Sinha, a professor of accounting at California State University, Long Beach, who filed a lawsuit last year challenging the university system’s addition of caste to its discrimination policy.

Opponents say that expressly naming caste as a protected characteristic disproportionately makes South Asians more vulnerable to unfair accusations of discrimination for actions that may have nothing to do with caste. They see redemption in the state dropping its case against the two managers at the heart of the Cisco case, though its lawsuit against the company is still ongoing.

The State Legislature, in an attempt to address such concerns, amended Senator Wahab’s bill this summer to make caste a subset of ancestry discrimination rather than its own class. But that did not satisfy critics. Some say that writing caste into state law will draw greater attention to outdated South Asian distinctions rather than dissolve them.

“We are all in America now and our kids are second- and third-generation,” said Samir Kalra, managing director for policy and programs at the Hindu American Foundation, one of the organizations leading the opposition. “As immigrants, we want to create a better society and lifestyle and leave all these issues behind.”

It is difficult to know how widespread caste discrimination is in the United States. A 2020 survey of Indian Americans conducted by the Carnegie Endowment for International Peace found that only 5 percent of respondents reported having encountered caste discrimination. The same survey found that Hindus born outside the country were significantly more likely than U.S.-born respondents to identify with a caste group.

Some people with Dalit ancestry have said they are hesitant to report discrimination for fear that it could jeopardize their visa status in the United States or invite retaliation. The bill’s proponents point out that caste bias is not confined to Hinduism, and is present in other religious communities.

“It’s not that caste is something that has just popped up,” said Sangay Mishra, an associate professor of political science at Drew University and the author of “Desis Divided: The Political Lives of South Asian Americans.” “As culture travels from India to the diaspora, as language travels, as cuisine travels, so does caste. We are just talking about a different scale now.”

Feelings remain intense on both sides of the bill. Proponents started a hunger strike this week that they said would last until Governor Newsom signed the legislation. Opponents have started a recall drive against Senator Wahab.

On a recent weekday, dozens of people, most of them first-generation immigrants, gathered at the State Capitol to rally in support of the bill. The group listened carefully as Thenmozhi Soundararajan, the founder of Equality Labs, a Dalit civil rights organization, coached them on how to answer questions about the measure. A picnic of chapati and chai waited on the grass nearby.

Backers have acknowledged that existing laws can be used to fight caste discrimination. But they say an explicit definition in state law would provide greater assurance for victims who want to speak out. And they believe that the bill would raise broader awareness about such bias and how it may surface — that questions about one’s dietary habits or parents’ occupations may be more than a matter of personal curiosity.

Among the supporters was Sunita Singh. Since moving to the United States from India in the early 1980s, Ms. Singh said she and her family had faced more discrimination based on race than on caste. She recalled how, after the Sept. 11 attacks, her son’s locker was glued shut at his high school because classmates thought he was Muslim.

But Ms. Singh said that caste discrimination was a problem, too. Not long after she arrived in America, members of her Ravidassia religious community, which has Dalit roots, were asked to use separate pots and pans at the Sikh temple that they had been renting in Central California.

For Ms. Singh and others in her group, the request evoked the practice, still found in parts of India, of having people of Dalit lineage eat with separate cups and plates to prevent them from “polluting” those used by higher castes.

The incident decades ago became the impetus for Ms. Singh and the other Ravidassia to establish their own temple. There are now six Ravidassia temples in California, and the community has been among the most vocal backers of the bill banning caste discrimination.

“We don’t want to be treated in this country any different than other Americans,” Ms. Singh said. “We want to be treated like humans.”