IT WAS less than a month ago that a spokesman for retired neurosurgeon Ben Carson told reporters that the erstwhile GOP presidential candidate would not be serving the Trump administration in anything but an unofficial advisory capacity. “Dr. Carson feels he has no government experience,” Armstrong Williams said, “he’s never run a federal agency. The last thing he would want to do was take a position that could cripple the presidency.” On that basis alone, President-elect Donald Trump’s announcement Monday that Mr. Carson would be his choice to head the Department of Housing and Urban Development was baffling. Add the fact that Mr. Carson has no relevant expertise whatsoever (secretary of health and human services, the previous job for which the highly accomplished physician was mentioned, might have been a different story) and Mr. Trump’s pick goes well beyond baffling.

[Donald Trump says he wants to fix cities. Ben Carson will make them worse.]

To be sure, HUD’s mission, in large part, is to help the urban poor through administering public housing, distributing rental-assistance vouchers and other programs; Mr. Carson’s Detroit boyhood certainly taught him what it is like to grow up poor in a segregated big city and to succeed against the odds. No doubt, too, the half-century-old HUD bureaucracy’s record is mixed at best, with more than a few scandals involving its various grants and subsidies. In that sense, a Republican administration could be expected to seek someone with fresh free-market-oriented policy alternatives. Mr. Carson, however, comes equipped with little more than the generalities about abolishing “dependency” that he spouted on the campaign trail. In an op-ed last year, he called new Obama administration regulations linking housing aid to more ambitious neighborhood desegregation efforts “government-engineered attempts to legislate racial equality” and suggested that they would be “downright dangerous.” As HUD secretary, he would be in charge of federal fair-housing enforcement.

Mr. Carson’s nomination is the second puzzling sign about where housing policy might be headed under the Trump administration. The first was Treasury Secretary-designate Steven Mnuchin’s comment that “we’ve got to get Fannie [Mae] and Freddie [Mac] out of government ownership. It makes no sense that these are owned by the government and have been controlled by the government for as long as they have.” That could mean Mr. Mnuchin will argue for a total overhaul of the government’s mortgage guarantee business that finally ends the system of private gain, public risk that prevailed before the government took over the failing Fannie and Fred in 2008. Or, it could be interpreted as support for the efforts, so far thwarted by courts and Congress, of hedge funds to make a killing through a Treasury-blessed “privatization.” Certainly it would help if the next HUD secretary were an expert on the housing market capable of weighing in against the more dubious plans being floated for Fannie and Freddie.

[Trump’s team of faux populists and real crony capitalists]

President-elect Donald Trump named Ben Carson as his nominee for housing and urban development secretary. Here's what you need to know about the former GOP presidential candidate. (Sarah Parnass,Osman Malik/The Washington Post)

Mr. Carson needs to be given a thorough, searching examination by the Senate over his approach to housing policy, which, though certainly not brain surgery, does present complexities that would challenge a nominee far more experienced than he.