ONE OF the most important functions the federal government performs is the decennial census, which not only provides a demographic snapshot of the country but also determines how much representation each state gets in Congress. It has been a thankfully nonpartisan effort in past years, run by experienced professionals who offered critics little basis on which to accuse them of tilting the count. The Trump administration might soon break that tradition.

The latest reason for concern came into view Tuesday, in a Politico report revealing that President Trump might name Thomas Brunell, a professor at the University of Texas at Dallas, to be deputy director of the Census Bureau. He would be a poor choice.

Though he is a serious academic, there is nothing in Mr. Brunell's background suggesting he is qualified to run a large government bureaucracy in general or the Census Bureau in particular. Previous Census Bureau leaders generally served extensively in government roles directly related to the bureau's work. Mr. Brunell has not.

These facts have led many to wonder why Trump administration officials might want Mr. Brunell running the bureau. The answer may lie in his past work helping Republicans in electoral map cases, or in some of his views on voting issues. Mr. Brunell has criticized partisan gerrymandering — but also early voting and nonpartisan redistricting commissions. Something of an iconoclast in his field, he is most notable among political scientists for arguing that electoral districts should be drawn to maximize the proportion of like-minded voters in each, limiting the number of competitive seats on electoral maps.

None of this proves that Mr. Brunell would run a partisan Census Bureau. But his political affiliations and previous work would nevertheless harm perceptions of the bureau’s integrity, an institution in which Americans must have complete faith. His possible appointment has inflamed preexisting worries that the Trump administration will meddle with the count. Of particular concern is the possibility that the president would order that census forms ask about immigration status, which would result in low response rates and, potentially, massive undercounts in minority communities.

Republicans in Congress have badly underfunded the census the past several years, leading the bureau to cancel or put off important programs, which could harm the quality of the 2020 count. This fact alone argues for picking Census Bureau leaders seasoned in government operations and ready to take on a huge management challenge.

Mr. Brunell, Politico reported, was considered for the Census Bureau’s top job, but opposition in Congress nixed that plan. Unlike candidates for the director’s job, those picked to be deputy director do not need Senate confirmation. If tapped, Mr. Brunell could start immediately, even while the bureau lacks a confirmed director. That would be damaging to an enterprise already at risk. Mr. Trump should find someone else.