EDINBURG, Texas — Next month, California will uncork a $187 million campaign to prod its nearly 40 million residents to participate in the 2020 census. Neighborhoods across the state have been computer-ranked by how likely residents are to fill out census forms. Custom marketing campaigns are being focus-grouped. Nonprofit organizations have been showered with grants to boost response in hard-to-count areas.

Texas has a campaign, too — a shoestring campaign. Although the state’s 29 million residents make it second in population only to California, the Texas Legislature has declined to spend any money to see that they are counted.A volunteer corps of civic groups, philanthropies, local governments and others are trying to fill the breach.

Time was when the census was a civic coming-together, with the states like 8-year-olds pressed against door jambs, awaiting the pencil marks that would show how they had grown. Now it’s goodbye to all that: Next year’s census is part head count and part power struggle, the most politicized population tally in a century, in which a state’s desire for an accurate count could depend on which party is in charge there.

Worried about an undercount, California and 25 other states are pouring close to a third of a billion dollars — an unheard-of sum — into pumping up response rates for the count next April.

They hope to maximize their population totals and, by extension, their share of federal resources and the size of their House delegations in future Congresses.

Equally remarkable, however, are the 24 states like Texas that are not spending a penny. The political divide is stark: Seventeen of those 24 are led by Republican governors and legislatures, including population heavyweights like Texas, Florida and Ohio. But of the 26 states that are spending money, only four are Republican-controlled.

Tight state budgets could be a factor. So could inertia; sinking millions of state dollars into census outreach is a fairly new idea. But few doubt that a prime factor is politics: An accurate census would include more people from harder-to-count groups like Hispanics, African-Americans, Asians and the poor who tend to vote Democratic.

If they do not participate, the population count would skew Republican — and so would political maps, based on census results, that legislatures will draw in 2021.

Next year’s head count already faces daunting challenges. A wave of immigration not seen since the early 1900s has brought into the country people who are either unaware of the importance of the American census or are suspicious of those that were conducted in their native countries. The 2020 count already has been tarred by a ferocious battle over Republican efforts to enumerate noncitizens nationwide, a fight that is likely to depress census response next year among minorities who are mistrustful of the government. The Census Bureau works to encourage participation, but this time around, its resources are spread especially thin.

Local leaders regard the tally as a once-in-a-decade chance to top up federal subsidies for crucial services like education and health care that are based on population. “We have this one shot,” said Erika Reyna-Velazquez, the assistant chief of staff to the Hidalgo County judge in Edinburg, Texas, in the Rio Grande Valley near the border with Mexico. “And if we miss it, we’re going to be undercounted again for the next 10 years.”

In Texas, a bill to commit $50 million to census response died this spring in the Republican-controlled Legislature. Representative César J. Blanco, the El Paso Democrat who sponsored the bill, claimed that the Legislature wanted to blunt a demographic shift that has strengthened Democrats. “They’re concerned that if you have a more accurate count, it would put them at a disadvantage,” he said.

That comes at a price, said Daniel A. Smith, a professor of political science at the University of Florida. “To send a political statement that you don’t want people to be counted, which might reduce the amount of federal funding your state gets, would seem to be cutting off your nose to spite your face,” he said.

Texans could need that money. The state adds more than a thousand new residents daily. Half are newborns. Nearly 30 percent hail from foreign countries, a hefty share from Asia.

The remaining 20 percent moved from other states, led by California, which is expected to lose a House seat for the first time ever — and which is sparing no expense to maximize its census tally. Although the Census Bureau publishes a map showing response to the 2010 census in all 66,000 census tracts, California commissioned its own map, ranking a tract’s expected census response according to 14 variables like education, income and housing type (a tract in Stockton, in the Central Valley breadbasket, is the toughest target).

For the first time, the 2020 census will be conducted largely over the internet; but in rural California, internet service is spotty. So the census message will be delivered according to its audience: at community events popular with farm laborers; on billboards in internet-scarce areas; via Facebook or text messages, whichever micro-targeted recipients use most.

The state is engaging trusted community groups to convince suspicious minority groups that the census is important and confidential. To reach the four in 10 Californians who are Hispanic, it gave $400,000 to the NALEO Education Fund, which hired five regional managers to train canvassers and show social-service workers how to spread the census message among their clients.

Texas is another story.

“In Texas, I have one regional census manager,” said Lizette Escobedo, who heads NALEO’s national census program. “We have our regional manager driving sometimes up to six hours to train the trainers to do this work.”

In some ways, Texas mirrors California: Four in 10 residents are Hispanic. One in four is deemed hard to count. One in 17 is an undocumented immigrant.

Texas, too, is spending to boost census response — just without state help. “It’s inexcusable how little the state of Texas has done to prepare for 2020,” said Ann Beeson, the executive director of the Austin-based nonprofit Center for Public Policy Priorities. “Fortunately, Texans themselves are stepping up to the task.”

The center and the Communities Foundation of Texas, a Dallas philanthropy, lead the effort to drum up responses. The foundation has raised $1.5 million for work in hard-to-count areas. The Hogg Foundation, another philanthropy, has contributed $2 million; the United Way, $1.5 million. Houston, Dallas and other big cities are mounting campaigns.

But outside the major metros, money and personnel are scarce.

“It’s not that philanthropies aren’t doing enough,” said Lila Valencia, the senior demographer at the Texas Demographic Center. “It’s just that it’s going to take so much more than we have.”

The office of Gov. Greg Abbott did not immediately respond on Sunday to requests for comment on the state’s policy concerning the census.

Hidalgo County, over a thousand square miles of scrub and urban sprawl on the Mexico border, has been here before. Officially, 866,000 people, almost all Hispanic, live here. Unofficially, county officials count more than a million.

The county sued the federal government after the 2010 census undercounted the area. In some places fewer than one in five households filled out forms. Residents refused to open doors to Puerto Rican census takers, whose accents marked them as strangers. Others never received forms because they used post office boxes, which the Census Bureau does not count as mailing addresses.

This time, the county will spend $300,000 on census response. But it has been planning for this moment since 2017.

For more than two years, civic groups, school leaders, businesses and others have convened with county officials to chart strategy. Planners overlaid the Census Bureau’s address list on aerial photographs of the county — and found 15,000 overlooked households. Every household that completes a census form increases the county’s share of federal money for schools, medical care and other needs. But completing those forms will be tough. Much of Hidalgo County is poor and rural; internet outside the urban strip that hugs Interstate 2 is sparse. And mistrust of the government is epidemic.

“It’s a horrible time here,” said Christina Patiño Houle, an organizer with the Rio Grande Valley Equal Voice Network. Between the controversy over counting noncitizens and the Trump administration’s deportation campaign, “fear of anyone affiliated with the government who could tear apart a family on a moment’s notice is pervasive.”

That is apparent in the colonias, mostly rural unincorporated subdivisions where families often build their own homes. Despite appearing on census lists as single addresses, many lots hold two and three households, extended families in trailers and outbuildings. Many are undocumented.

In one colonia on the county’s west side, a 36-year-old undocumented immigrant named Maribel wanted little to do with the census. “The information goes to the government, and I don’t feel safe because of the administration, our president,” she said. “The Hispanic community is afraid to say their names and how many people are living with them.”

But the county is trying win over colonia residents. Catholic nuns at a community center have been recruited to hand out fliers and reassure them that the census is confidential. The county has outfitted a trailer with computer terminals, a mobile census station that will roam subdivisions next year. One selling point: If residents complete the census online, no one will knock on their doors later.

Martha Sanchez, a local leader with the advocacy group La Unión del Pueblo Entero, has a different approach: bingo games, popular in colonias, accompanied by a census sales pitch and census-themed bingo cards. “One of the cards is like, ‘This information has to be on the president’s desk,’” Ms. Sanchez said, “‘and the good thing is that our president doesn’t like to read, so do not fear the questionnaire.’”

Hidalgo County’s ambitious efforts are paralleled elsewhere in Texas — and in other states where governments are not ponying up money.

What’s not clear is whether even ambitious efforts can produce an accurate count.

The Bauman Foundation, a Washington philanthropy focused on democracy issues, has marshaled some 90 donors and hundreds of organizations to promote the census in cash-starved states. The foundation could raise $80 million nationally — and still fall short.

“There are so many gaps,” said Gary Bass, its managing director. When the census ends, he said, “I can imagine our funder community coming to me and saying, ‘Oh my god, we did something unprecedented. And it came out worse.’”

Michael Wines reported from Edinburg, Texas, and Dallas. Jose A. Del Real reported from Los Angeles.