Did the 2020 Census Undercount the Hispanic Population?

Adam Kincaid, executive director of the National Republican Redistricting Trust and Mr. Holder’s counterpart, said the gaps between the census projections and the final numbers raised suspicion about the figures and could diminish trust in the census, and in government in general. Arizona, Florida and Texas each received one House seat fewer than had been anticipated, and Minnesota, New York and Rhode Island each received one more seat than had been expected.

The Census Bureau, Mr. Kincaid said, has not been transparent about why its projections were off by so much in those states.

“It’s injecting more uncertainty into an already uncertain process,” Mr. Kincaid said in an interview Wednesday. “At a time when overall American faith and confidence in the government is low, this census is only going to exacerbate that.”

The bureau said last October that it had accounted for 99.7 percent of the nation’s housing units.

Tom Bonier, the chief executive of TargetSmart, a Democratic data firm, said that if the lower-than-expected gains in border states were the result of large undercounts, especially among Latinos, the Hispanic populations would be harmed. “What you’re going to see is a decrease in representation for those communities and a decrease in funding for those communities,” he said. “That makes it easier for Republicans to draw favorable maps for themselves in those states.”

Because the counting process was delayed by snags in the data-processing effort, the Census Bureau will not release race and ethnicity data until September. Once those figures have been reported, legislatures and commissions will be able to begin drawing boundaries for congressional and state legislative districts, a crucial political process that is the center of persistent partisan acrimony because it can determine the balance of power in Congress.

The results may be a high-stakes example of states’ getting what they paid for.

Arizona, Florida and Texas all had census self-response rates below the national average, which was 67 percent, according to the Census Bureau. California, which spent $187 million on a campaign to encourage its residents to complete the census forms and has the largest Hispanic population in the country, had a self-response rate of 70 percent. Still, the state lost a congressional seat for the first time in its history.

Minnesota, which led the nation in self-response rate at 75 percent, started its campaign five years early, building a coalition of more than 300 organizations and local governments that contacted more than 1.3 million people — about 23 percent of the state’s population.