Judge Furman rejected a claim that Commerce Secretary Wilbur L. Ross Jr., who made the decision to add the question to the census form, lacked the authority to do so. But the judge said the circumstances surrounding Mr. Ross’s actions, including his shifting explanation of what he did and why, raised questions about his true intent.

Mr. Ross originally said he acted at the request of the Justice Department, which he said needed better citizenship data to enforce the 1965 Voting Rights Act. But he later admitted — and Commerce Department documents confirmed — that he had discussed the citizenship question with administration officials from almost the beginning of his tenure in the department, and that he or his aides had asked the Justice Department to request that the question be added.

That alone does not prove that adding the question was intended to discriminate against immigrants, Judge Furman stated, but the sequence of events does raise suspicions.

Judge Furman added that those suspicions were bolstered by President Trump’s “racially charged” statements singling out immigrant minorities. Among them, he wrote, were Mr. Trump’s reference in January to “these people from shithole countries” who come to the United States; his claim in February that some immigrants “turn out to be horrendous” and are not “the best people;” and his statement in May that certain people trying to enter the United States “aren’t people, these are animals.”

While none of those statements refer directly to the citizenship question, the judge wrote, indications that Mr. Trump may have been personally involved in the deliberations over the question “help to nudge” the plaintiffs’ claim of intentional discrimination “across the line from conceivable to plausible.”