A group of Senate Democrats is requesting a hearing to dig into the 2020 census after the Trump administration announced this week it would include a question on citizenship.

Democrats sent a letter on Friday to Sen. Ron Johnson Ronald (Ron) Harold JohnsonThis week: Supreme Court fight over Ginsburg's seat upends Congress's agenda GOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate MORE (R-Wis.), the chairman of the Homeland Security and Governmental Affairs Committee, asking that he schedule the public hearing "at the soonest possible time" and that Commerce Secretary Wilbur Ross Wilbur Louis RossTrump 'very happy' to allow TikTok to operate in US if security concerns resolved TikTok, WeChat to be banned Sunday from US app stores The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE, who announced the change, be asked to testify.

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"We are deeply concerned about the recent announcement by the Commerce Department that it plans to add a new question to the 2020 Census that will ask respondents about their citizenship. We also remain concerned by well-documented management and operational challenges facing the Census Bureau," they wrote.

Democratic Sens. Kamala Harris Kamala HarrisJoe Biden looks to expand election battleground into Trump country Fox's Napolitano: Supreme Court confirmation hearings will be 'World War III of political battles' Rush Limbaugh encourages Senate to skip hearings for Trump's SCOTUS nominee MORE (Calif.), Tom Carper Thomas (Tom) Richard CarperDemocrat asks for probe of EPA's use of politically appointed lawyers Overnight Energy: Study links coronavirus mortality to air pollution exposure | Low-income, minority households pay more for utilities: report OVERNIGHT ENERGY: Democrats push resolution to battle climate change, sluggish economy and racial injustice | Senators reach compromise on greenhouse gas amendment stalling energy bill | Trump courts Florida voters with offshore drilling moratorium MORE (Del.), Gary Peters Gary Charles PetersBiden's six best bets in 2016 Trump states GOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate MORE (Mich.) and Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (Mo.) signed the letter.

The senators added that it was "essential" that Ross explain the "process, testing and analysis" behind adding a citizenship question and its impact on the planning for the 2020 census.

In addition to Ross, they also want acting Assistant Attorney General John Gore to testify, saying they believe he was "personally involved" in the decision. They also want a second group comprised of Census Bureau staff, stockholders and government watchdogs to assess planning for the 2020 census.

The Commerce Department announced on Monday evening that it would include a citizenship question in the next decennial survey. Ross, at the time, called it a "long-standing historical practice," though it has not appeared on the full census since 1950.

The move has enraged Democrats. Including a question on citizenship, they warn, could lower participation in immigrant communities and impact how federal resources are allocated or the size of a state's congressional delegation.

The four Democratic senators warned in their letter on Friday of the "risk of substantial undercount of persons" and that the decision to add the question is "tainted by improper political considerations."

The Department of Justice, under Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE, reportedly pushed for inclusion of the question.

Democrats have introduced legislation to block questions on citizenship or immigration status from being included. But they face an uphill battle to getting a bill through the GOP-controlled Congress.

Democratic attorneys general in several states, as well as progressive outside groups, have also pledged to bring legal action against the decision.