The court's decision on Tuesday was just the latest move in a complex saga.
The legal battle has focused on whether the Commerce Department, which oversees the Census Bureau, had followed federal law when it set a Sept. 30 deadline. But the subtext of the case has always been whether a cut-short count could be accurate enough to serve as the basis for determining political representation and the distribution of government funds.
The deadline for completing the count has moved several times, at first because of the coronavirus pandemic, which all but shuttered many census operations -- in which Census Bureau workers often go door-to-door to count hard-to-reach people -- last spring.
But in August, Wilbur L. Ross Jr., the commerce secretary, ordered that the deadline be moved up to Sept. 30 from Oct. 31, saying that the move was necessary to deliver preliminary information to Mr. Trump by the deadline demanded by law. Mr. Ross's move was made over objections from career census experts who argued that it could completely undermine the accuracy of the count.
Updated Oct. 14, 2020, 4:42 p.m. ET
What happens next?
Lawyers for the plaintiffs in the lawsuit, which was originally filed to stop Mr. Ross from compressing the length of the census count, said they would turn to making sure that the Census Bureau was not forced to make further cuts in accuracy checks during the monthslong period in which population data is processed and verified.
And experts have cautioned that the Supreme Court's order allowing for the early stoppage could not only harm the accuracy of the count, but also erode the public's trust in it.
Terri Ann Lowenthal, a longtime census expert and consultant to several groups pressing for an accurate tally, charged that the disarray caused by the administration's handling of the count "inevitably will undermine whatever public confidence remains in the census results."
The administration "could do the right thing, and allow those operations to wind down in an organized way over the next two weeks, or it could continue to push for rushed results, accuracy and quality be damned," she said.
Kristen Clarke, the president of the Lawyers' Committee for Civil Rights Under Law, which represents many of the parties that sued, said the decision would cause "irreversible damage to efforts to achieve a fair and accurate census."
How is the count going?
Despite many obstacles, the Census Bureau has mounted a dogged effort to fill in some of the tally's gaps. It has moved more than 16,000 census takers from places where it considers the count completed, sending them to states where the response is lagging, notably in the Deep South.
But to meet the earlier deadline that Mr. Ross had ordered, the Census Bureau scaled back some verification procedures and allowed census takers to accept less reliable information -- such as a neighbor's word on who lives in an uncounted house -- earlier in the process.
That allowed the bureau to report on Saturday that it had tallied 99.9 percent of all the nation's households. That so-called completion rate is new; past censuses used more conservative measures.
Experts say the 99.9 percent completion estimate may mask gaping holes in the count's coverage. While the bureau has not detailed what households the measure covers, it does not represent households that have actually filled out census forms. Rather, it appears to include those checked off the list of uncounted households by any means, however inaccurate.
Are there any other fights over the census this year?
In this highly unusual year, the wrangling over how long the census should be carried out is not the only battle over the count.
In July, the Trump administration announced that it would try to exclude people who had entered the country illegally from the population totals it sent to Congress for determining how many seats each state gets in the House of Representatives. Not counting those in the country illegally would exclude millions of people from the calculations and would most likely shift several seats from Democratic states to Republican states.
The Constitution requires congressional districts to be apportioned "counting the whole number of persons in each state," using information from the census, and a federal court ruled last month that the administration's move was illegal. The Supreme Court could hear an appeal from the administration as soon as December.