WASHINGTON, April 23 (Reuters) - The U.S. Supreme Court, in one of the most consequential cases of its current term, on Tuesday will hear the Trump administration's bid to add a citizenship question to the 2020 census, a plan opponents have called a Republican effort to scare immigrants from taking part in the population count.
Lower courts have blocked the question, ruling that the administration violated federal law and the U.S. Constitution in seeking to include it on the census form. The nine Supreme Court justices will hold an extended 80-minute argument session in the administration's appeal, with a ruling due by the end of June.
The case comes in a pair of lawsuits by a group of states and localities led by New York state, and a coalition of immigrant rights groups challenging the legality of the question. The census forms are due to be printed in the coming months.
The official population count, as determined by the census, is used to allot seats in the U.S. House of Representatives and distribute some $800 billion in federal funds.
Opponents have said inclusion of the question would cause a severe undercount by frightening immigrant households and Latinos from filling out the census, fearful that the information would be shared with law enforcement. This would cost Democratic-leaning areas electoral representation in Congress and federal aid, benefiting Republican-leaning parts of the country, they said.
President Donald Trump, a Republican, has pursued hardline immigration policies. His administration said the citizenship question would yield better data to enforce the Voting Rights Act, which protects eligible voters from discrimination.
Business groups and corporations such as Lyft, Inc, Box, Inc, Levi Strauss & Co and Uber Technologies Inc also opposed the citizenship question, saying it would compromise census data that they use to make decisions including where to put new locations and how to market products.
Manhattan-based U.S. District Judge Jesse Furman on Jan. 15 ruled that the Commerce Department's decision to add the question violated a federal law called the Administrative Procedure Act. Federal judges in Maryland and California also prohibited the question's inclusion in subsequent rulings, saying it would violate the Constitution's mandate to enumerate the population every 10 years.
Furman found that Commerce Secretary Wilbur Ross, whose department includes the Census Bureau, concealed his true motives for his March 2018 decision to add the question.
The Census Bureau itself estimated that households corresponding to 6.5 million people would not respond to the census if the citizenship question is asked, leading to less accurate citizenship data.
Citizenship has not been asked of all households since the 1950 census. It has featured since then on questionnaires sent to a smaller subset of the population. While only U.S. citizens can vote, non-citizens comprise an estimated 7 percent of the population.
For a graphic on the major Supreme Court cases this term: tmsnrt.rs/2V2T0Uf
Reporting by Andrew Chung and Lawrence Hurley; Editing by Will Dunham