Shortly after the Supreme Court ruled that the Trump administration can end the 2020 census, a text message went out to field supervisors in Northern California telling them to start collecting the iPhones their census takers use for gathering household information during their door-knocking.

It was the fifth time in two months that they were given a new end date — this one Thursday — for the head count of everyone living in the U.S.

The Supreme Court decision Tuesday was just the latest case of whiplash for the census, which has faced starts and stops from the pandemic, natural disasters and...