The Census Bureau plans to finish collecting data by the end of September, a month earlier than expected, raising concerns that the 2020 Census might not have time to count everyone before the deadline. 

At this point in the process the Census Bureau is tasked with reaching approximately four out of 10 households in the country that have not already responded online or by mail, a process that has been partially delayed due to the coronavirus pandemic. 

In a normal census, workers would canvas neighborhoods and conduct door-to-door outreach to households that haven't responded and raise awareness about the importance of submitting the information, especially among communities that are typically undercounted. The coronavirus pandemic has already made that more complicated and now Democrats and advocates are concerned that speeding up the Census will make it impossible to accurately represent people of color, low-income communities and rural populations. 

The Census Bureau confirmed Monday night that it plans to change the timeline for data collection to end on Sept. 30. They plan to hire and train more census workers and offer incentives for them to work more hours, saying the plan intends to reach the same number of household responses as in prior censuses. 

But there's no precedent for door-to-door census operations during a pandemic, census workers could need more time to get to all households or families could be more reluctant to answer the door or speak to a census worker. Given that 40% of census data is collected in person, Sarah Brannon, managing director of the ACLU's Voting Rights Project, said she doubts the Census Bureau will be able to reach everyone under the new timeline.

"I think it would be extremely hard, I would be skeptical that they can do it," she told ABC News. "The ACLU is skeptical that anything can be done except give them more time to do what they traditionally do and have traditionally done in past years with pretty good success." 

Part of the challenge is also that the Census Bureau is on a deadline that only Congress can change. It is legally required to finish collecting and analyzing data to report it to Congress by Dec. 31. Officials from the Department of Commerce overseeing the census said in July that they were already past the window of being able to get an accurate census count without an extension, but Congress has not yet passed anything to push back the deadline.

Populations that are considered hard to reach, like low-income communities, people of color, indigenous populations and immigrants, are further behind in responding to the 2020 census than they were in 2010, according to an analysis by the UCLA Center for Neighborhood Knowledge, and experts are concerned speeding up the timeline will make it harder to make up the gap for those groups.

"I believe that ending the enumeration a month early (relative to the previous modified schedule) will be an unprecedented disaster for people of color and low-income people. Our continuing monitoring indicates that there is still a huge gap between advantaged and disadvantaged neighborhoods," Paul Ong, the center's director and a former Census Bureau adviser, said in an email. 

Ong said the Census Bureau needs to focus equally on a high response rate and making sure they aren't reaching some groups more than others, especially since census data is used to determine congressional representation and distribution of federal resources undercounting those groups could mean that the same communities hit hardest by COVID-19 are further disenfranchised going forward. 

"There are enormous political and economic implications from a racially biased census counted. Marginalized populations will be further disenfranchised and disproportionately left out for public funds and services," he said in the email. 

Democrats and advocacy groups like the Leadership Conference on Civil & Human Rights say this is the latest move from the Trump administration to politicize the census by pushing down participation and forcing the census bureau to skip households. President Donald Trump has also sought to include a citizenship question on the census, which has since been abandoned, and to use census data to exclude undocumented immigrants from being included when determining congressional districts.

House Democrats have proposed extensions in the HEROES Act, but it has not moved in the Senate since being approved in the House. The Republican proposal for coronavirus relief in the Senate, the HEALS Act, does not include language about the census.