Transcript for Trump fights back after Supreme Court rejects census citizen question
supreme court delivering two decisions today, including a major blow to the trump administration. Chief justice John Roberts, the deciding factor, blocking the white house from adding a citizenship question to the 2020 census. President trump calling the decision, quote, totally ridiculous and now threatening to delay the census. ABC's senior national correspondent Terrill mour ran is at the supreme court. Reporter: Tonight, president trump is already fighting back against the supreme court census decision, tweeting from Japan -- "I have asked the lawyers if they can delay the census, no matter how long, until the supreme court gets additional information." The trump administration was planning to add a question to the 2020 census, asking every person living in the U.S., are you a citizen? Can you imagine, you send out a census and you're not allowed to say whether or not a person is a American citizen? Reporter: But the census bureau itself estimated that millions of people, mostly minorities, would decline to answer that question and go uncounted by the census. A crucial issue since the census is used to decide how many seats each state gets in the house of representatives, and how federal spending is distributed. Chief justice John Roberts, joining the four liberal justices, hammering the administration's claim offered by commerce secretary Wilbur Ross that they added the question only to help enforce the voting rights act. Roberts calling that "Contrived" and a "Distraction," writing -- "The evidence tells a story that does not match the explanation the secretary gave for his decision." That stinging rebuke announced after Roberts sided with his conservative colleagues, ruling that federal courts do not have the power to intervene and stop even the most extreme forms of partisan Gerry mannering. Lawmakers in several states have been using census data to draw congressional districts for openly partisan reasons, as one powerful legislator admitted in North Carolina. I propose that we draw the maps to give a partisan advantage to 10 Republicans and 3 Democrats because I do not believe it's possible to draw a map with 11 Republicans and two Democrats. Reporter: Justice Elena Kagan, in an emotional dissent -- "In giving such gerrymanders a pass from judicial review, the majority goes tragically wrong." While the court said its willing to consider another version of this case, the clock is ticking. Tom? Terry Moran for us tonight. Terry, thank you.
This transcript has been automatically generated and may not be 100% accurate.