The White House was widely expected to make a public announcement about the position early this year, with officials floating a senior administration lawyer, Jim Carroll, as a likely replacement for Kirstjen Nielsen, a close Kelly confidante who accompanied him from the Department of Homeland Security to the West Wing last summer before the president tapped her to become DHS secretary.

But while Carroll has assumed some of the responsibilities of Nielsen’s old job, Kelly has been disappointed in his performance and has held back on officially bestowing the title, according to two administration officials.

Kelly’s struggle to replace his own team members is perhaps the clearest illustration of the problems he faces trying to keep President Donald Trump’s administration staffed as officials who joined in the first year leave.