Officials warned that Wilbur Ross' order shortening census schedule could make it seem politically manipulated

The revelations are in an expansive set of internal Census Bureau and Commerce Department records produced Saturday by the Trump administration, which is defending in the courts its plan to end 2020 census counting on September 30, rather than October 31. A CNN review of nearly 15,000 pages of documents revealed previously unreported details from emails, memoranda, instant messages, presentations and briefings that show how the decision developed behind the scenes.

The officials -- top-ranking, career statistical professionals at the Census Bureau -- prepared to send their director before Congress on July 29 with a plea for more time. Even technological improvements, they wrote in his notes, "will not enable us to meet the statutory deadlines based on projected current field completion dates."

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Director Steve Dillingham didn't deliver that message. Instead, he told lawmakers he was "aware that discussions have been held between the administration and Congress" but that he was "not involved directly."

By that point, Ross, who oversees the Census Bureau, had directed officials to show him within days how they would condense the counting effort.

Census experts reasoned the last possible day to have government employees knocking on doors around the country was September 30. That would give statistical workers just three months to crunch the numbers, remove duplicate responses, search other databases to count households that had not responded, scour for anomalies and present numbers to President Donald Trump by December 31.

The extension until April that Census Bureau officials wanted -- and the Trump administration had earlier supported -- might mean a new occupant of the Oval Office, who could overturn the controversial Trump directive to exclude undocumented immigrants from the final figures. That directive has since been blocked by a panel of federal judges and the Trump administration is appealing to the Supreme Court.

The final apportionment figures are used to divide up the seats in Congress, determine presidential electoral votes and determine in which states and communities billions of federal dollars are spent.

The coronavirus pandemic made their work tougher, a team of senior officials wrote in a memo. They believed submissions would "require additional data processing to ensure people are accurately counted in the correct location." Condensing the operations would "run the risk" of errors and "additional legal challenges" to the figures "as a result of diminished quality."

In early July, Census officials were briefing members of Congress about the challenges they faced, including a committee that determines how much funding federal agencies receive.

By July 21, Census officials wrote they had "developed a plan in response to Secretarial direction" to meet the December 31 deadline. It included ending counting in September, then "compressing and streamlining backend processing."

But they appeared uncertain which deadline Ross, the commerce secretary, would choose.

On July 23, Kathleen Styles, a Census Bureau official who oversees relationships with outside groups, wrote to her colleagues that "the situation will change in the coming days," but that it was worth spreading the message about the risks to an abbreviated count.

The memo she and colleagues wrote left no question about their position.

"High Level Message," it read. "Curtailing census operations will result in a census that is of unacceptable quality."

The "full 120 days" extension "that the Administration originally requested" would be "the best change to produce high quality, useable census results in this difficult time," the memo added.

The bureau, it noted, had pulled Census employees out of the field because of the pandemic, and changed procedures "intended to produce the most accurate census possible, and cannot be rushed without diminishing data quality or introducing unacceptable risk to either operations or field staff."

The early end to operations meant enumerators, who knock on the doors of households that have not yet responded, would have to go out even when the coronavirus was not under control in their area.

Enrique Lamas, a senior adviser in Dillingham's office, asked officials to consider whether they would indeed "send staff out to all locations (regardless of covid levels)" in the next several days.

"I think that is a big decision and we need to (be) clear," he wrote.

About a week after the alarming memo from Styles and her colleagues, Ross instructed Census Bureau officials to present to him in just four days a way to conclude counting on September 30.

Census officials held calls and exchanged plans until nearly midnight that Saturday and Sunday to present him with a plan at 8 a.m. on August 3. The announcement of the September deadline came later that day.

As Census field operations leader Jamey Christy wrote in an email, the "acceleration" was underway.