President Trump spoke out strongly Monday in favor of a contentious citizenship question that his commerce secretary added to the 2020 Census, asserting that the survey would be “meaningless” without the addition.

In a morning tweet, Trump blamed “Radical Democrats” for trying to remove what he termed “the all important Citizenship Question” that has been derided by advocates for immigrants.

“Report would be meaningless and a waste of the $Billions (ridiculous) that it costs to put together!” Trump said in his tweet.

Two federal judges have already ruled against the question. The Supreme Court is set to hold a hearing on it April 23 and is expected to rule on it by June, shortly before the survey forms are due to go to the printer.

Publicity materials distributed at a Census Bureau news event Monday included the citizenship question on a list of questions the survey asks, with no mention of the fact that it would be illegal to ask the question on the decennial census.

At the event, Census Bureau director Steven Dillingham declined to discuss the president’s tweet about the question.

Opponents have characterized the question as a political maneuver by the Trump administration. They say its inclusion, particularly at a time when noncitizens feel targeted by the government, will deter many immigrants and their family members from participating, reducing the count’s accuracy and harming people who live in areas with large immigrant populations.

Census data is used to allocate hundreds of billions of dollars in federal funding and to determine apportionment and redistricting.

Commerce Secretary Wilbur Ross has maintained that the information is important for several reasons, including enforcement of the Voting Rights Act, and that he carefully considered the advantages and disadvantages of adding the question before making his decision.

Ross was grilled during a House hearing last month on his rationale for adding the question, which was generally defended by Republicans.

Democrats pointed to congressional hearings last spring at which Ross testified that his move to add the question came solely in response to a December 2017 request from the Justice Department.

Litigation around the question later produced emails showing that Ross, who oversees the Census Bureau, had been pushing for the question for months before that.

One of the federal judges who ruled against adding the question also took issue with Ross’s motives and said the secretary broke a “veritable smorgasbord” of federal rules by overriding the advice of career officials to not include the question.

Trump’s tweet drew criticism Monday from Democrats, including Rep. Adam B. Schiff (D-Calif.).

“Doing what the Constitution requires and counting every person is not ‘meaningless’ and it is surely not a ‘waste,’ ” he wrote in a tweet directed at Trump. “Including a citizenship question will only suppress participation and, inevitably, result in inaccurate data. But, of course, that’s exactly why you want to do it.”

Robert Barnes contributed to this report.