Leaders of advocacy groups warned lawmakers on Thursday that the fight over a failed citizenship question, the digital divide and the wording of questions on Hispanic origin and race may lead to the undercounting of some communities during the 2020 Census.

The leaders from ethnic advocacy groups and civil rights organizations also testified before the House Committee on Oversight and Reform that they worried the U.S. Census Bureau was falling behind in hiring workers and that its media campaign wasn't going to be robust enough.

The Census Bureau says the hardest people to count are young children, racial and ethnic minorities, non-English speakers, i mmigrants living in the country illegally, the homeless and low-income people.

The once-a-decade head count will determine how $1.5 trillion in federal spending is allocated among the 50 states and how many congressional seats each gets. The count starts in tribal communities in northern Alaska in less than two weeks . Res idents in the rest of the country can start participating starting in the middle of March.

“The 2020 Census is likely to be the largest and most difficult enumeration ever," said Vanita Gupta, CEO of the Leadership Conference on Civil & Human Rights. “There are no do-overs. We need to get it right the first time.”

Even though the U.S. Supreme Court last summer blocked the Trump administration from adding a question on the 2020 form about whether a respondent is a citizen, the topic came up repeatedly during Thursday's hearing.

House Republicans argued that it's important to know how many citizens live in the U.S.

"It's important for us to know as a country how many of us are citizens," said U.S. Rep. Jody Hice, a Republican from Georgia. “What I get annoyed at is how that issue is used to attack the president.”

But House Democrats, and several of the hearing's witnesses, said the earlier fight over the citizenship question may still discourage immigrants and Hispanics from participating this spring.

"We had a five-alarm fire, and even though we put the fire out through litigation, we need to know what damage has been done," said John Yang, executive director of Asian Americans Advancing Justice. “Like with a fire, the damage that has been done needs time to be repaired.”

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