LIEUTENANTS OF Mayor Barry may do all the strained explaining they wish, but when hundreds of laid-off city employees are left in the dust while the wife of the mayor's top political adviser gets a $25,000-a-year city government job, the excuses do pale. How does a RIF victim accept this, anyway? Answer: not well.

The issue, says D.C. Council member Betty Ann Kane, is "a moral one"--and that's the point: it doesn't matter that Winifred Donaldson, wife of Ivanhoe Donaldson, was unaware of the circumstances when she "just applied for a job" as a special assistant to the city's water registrar in the Department of Environmental Services; and it doesn't matter that she "never discussed" the job with her husband, who, until he quits next month to run Mr. Barry's re-election campaign, is acting director of another city department.

In fact it doesn't even matter that Mrs. Donaldson's years in government, on Capitol Hill and more recently in the business of real estate may be top qualifications for handling complaints about water billing and doing some research. Besides, Mrs. Donaldson shouldn't be faulted for seeing a job and going for it.

But Mayor Barry, who said he didn't know what Mrs. Kane was talking about, had better start talking himself about making some changes in the hiring system. His personnel director, Jos,e Guttierez, says the job in question was a temporary one and therefore didn't need to be posted--and it wasn't; because it is temporary, he says, even people on the "priority list" of those laid off by RIF are not automatically considered. "They have to come in and specifically apply for temporary positions and then we would have to examine their qualifications . . ."

In the federal government, as we read it in Mike Causey's "Federal Diary" column the other day, there is a regulation that entitles a RIFed career employee on the re-employment list to displace a temporary or intermittent worker if the career employee is qualified.

That's fair enough, and if Mayor Barry has a sense of fairness--not to mention a political sense-- he will move quickly to enforce such a policy.