CONTINUITY TENDS to be a problem toward the end of any administration. Some Cabinet and sub-Cabinet officers leave while the leaving's good, to make the most of their visibility and service; others leave because, for one reason or another, they must. The vacancies that occur are hard to fill because all further appointments are short-term. For this and other reasons, the latter part of an administration can be pretty ragged.

In this context the nomination of Ann Dore McLaughlin to succeed Bill Brock as secretary of labor is a constructive act. It is no secret that Mrs. McLaughlin was chosen in significant part because a) she is a woman and the administration thinks it needs a woman in the Cabinet to replace Transportation Secretary Elizabeth Dole, and b) her nomination seemed likely to be noncontroversial. The other leading candidate for the job, Office of Personnel Management Director Constance Horner, had drawn some grumblings from organized labor. These emanated mainly fromthe federal employee unions and seemed pretty petty to us; Mrs. Horner has done a good job.But the administration didn't want to pick the fight.

But Mrs. McLaughlin has (as Mrs. Horner would have had too) this other virtue from our standpoint: she seems likely, on the strength of her performance twice before in the administration, as assistant secretary of the Treasury and undersecretary of interior, to carry forward the same rational approach to the labor agency's problems and programs that Mr. Brock brought there. He took over a dismembered department and restored its balance and place at the policy tables. On issues as di-verse as occupational safety and health and affirmative action, he eased it back within the zone of reason. If Mrs. McLaughlin can learn enough, fast enough, to keep it there for the 14 months that remain, she will have performed an important service.