The truth is, Democrats don’t care about the integrity of the census. To them, political calculations are more important than the population count. Democrats believe that asking the citizenship question on the census will cause them to lose power in Washington. This is because the census is used to reapportion Congressional seats, and Democrats know that Congressional apportionment according to the population of citizens, rather than total population, will cause them to lose seats in Congress.
https://www.foxnews.com/opinion/reps-jordan-and-meadows-democrats-dont-care-about-the-integrity-of-the-census