It hasn't yet appeared in those help-wanted ads that President Reagan keeps talking about, but Maryland's Republican Party has had quite a time trying to fill a key vacancy in its ranks. Though the job in question has only the loosest of qualifications, there's been something less than a stampede to become the next Republican candidate for governor. In fact, the talent hunt has been reduced to combing and wooing recent converts from the Democratic Party, none of whom has exactly jumped at the opportunity to carry a new standard into battle. Every now and then, when some possible hopefuls have expressed mild interest they have wound up in an Alphonse-Gaston routine over who should throw a hat in the ring and then have made hasty, deferential retreats.

At least the Republicans were able to sign up some help for the Senate race. Former White House official Linda Chavez and Baltimore businessman Richard Sullivan have entered the GOP contest, with the winner set to face the survivor of what already is turning into a lively Democratic contest for that party's nomination. Among the Democrats yearning to be a senator is the man who already is the governor, Harry Hughes, as well as two members of Congress, Reps. Mike Barnes and Barbara Mikulski, and Baltimore County Executive Donald Hutchinson.

For governor, the latest man to be courted by GOP recruiters is Delegate Thomas J. Mooney of Prince George's County. He has two intriguing qualifications for the governor's race: 1) last fall, he switched from the Democratic Party, and 2) in December, he announced he would seek the Republican nomination for the Senate. Why didn't he go then for governor?

Here the going, or non-going, gets difficult: Mr. Mooney said he didn't wish to get into a contest with Howard County Executive Hugh Nichols, who is a good friend and, by the way, another former Democrat. That was before Mr. Nichols stepped out, believing that Dr. Aris T. Allen would run. Dr. Allen said no, too, deferring to what he thought was Mr. Nichols' desire to get back in the race.

However comforting it may be to know that Maryland Republicans -- new as well as lifetime -- get along so well with each other, all this fellowship and good will is killing them -- and the two-party tradition to boot.