With a little less than two months to go before Maryland's primary election, it's time for the first campaignspeak award. It goes to Baltimore Mayor William Donald Schaefer and his campaign staff for the convoluted explanations that followed Schaefer's abrupt departure last week from what was to be a two-hour radio debate with Attorney General Stephen H. Sachs.

The mayor, who had declined to appear the week before, made a sudden appearance at the debate, but then cut out at halftime.

Set aside arguments over whether the debate donnybrook on station WBAL proved that Schaefer is imperious and arrogant, or that his principal opponent in the Democratic primary race is a crybaby and a name-caller.

Instead, consider the tortured reasoning of the Schaefer camp about the incident.

First, the facts. According to the ground rules set by the Baltimore League of Women Voters and WBAL, candidates had until July 2 to accept the invitation to the debate. There was to be one hour of questioning from a panel of reporters and a league official and a second hour of questions from listeners and among the candidates.

On July 3, the Schaefer campaign officially declined the offer to participate. On the night of the debate, July 10, Schaefer arrived unannounced at the studio shortly before air time and said he would stay only for the first 50 minutes because he had to attend a meeting of the Mount Royal Democratic Club.

When the mayor departed midway through the broadcast Sachs angrily accused Schaefer of breaking the rules to suit his own purposes and of avoiding direct questions from Sachs and Lyndon H. LaRouche Jr. candidate Lawrence Freeman. The mayor's flouting of the rules was symptomatic of his approach to government, Sachs charged.

Schaefer campaign spokesman Bob Douglas and the mayor said the WBAL debate was the third such forum for candidates in nine days. There had been earlier forums July 1, the first hosted by female legislators, the second by the Maryland Food Committee.

At the first, candidates answered questions submitted to them in advance and had no opportunity to confront their opponents. At the second, each candidate made a five-minute presentation on hunger. All were against it. There were no questions.

So much for three debates.

Douglas also said that "the mayor abided by the format of the debate until Mr. Sachs at the end began calling the mayor names," an assessment that ignored the mayor's stated intention to leave early.

"The mayor doesn't view his participation as having stayed for just half of the debate," said Douglas. "The mayor stayed for the structured part . . . . He was dragged away from a healthy, robust, 55-minute discussion by Mr. Sachs' name-calling." Those present said Schaefer left under his own power.

And finally, Douglas said the mayor did not break the rules because the rules did not specifically forbid a candidate from showing up after declining and also did not specify that candidates had to stay for the whole shebang. Douglas will no doubt make an excellent attorney, as he plans to do after concluding his stint as spokesman for the campaign.

One wonders, however, what the Bob Douglas of four years ago would have said had front-runner Harry Hughes walked out halfway through the 1982 gubernatorial primary debate televised by WMAR-TV in Baltimore. Douglas was the WMAR producer who organized that one.

The irony of the debate flap is that Schaefer's sneak attack, which Douglas said was the mayor's spontaneous idea and not part of a grand strategy, worked splendidly for the first 50 minutes.

Candidates tend to plan their debate speeches and responses meticulously, and Schaefer's sudden arrival forced Sachs to throw out his playbook and wing it.

Sachs ended up ad-libbing his opening statement, because most of what he had planned to say was about Schaefer's not being there.

For much of the first part of the debate, Sachs was off his game, and Schaefer ably exploited the element of surprise. The mayor was poised, reasonable and stuck to his theme that he has the long experience necessary to be governor.

Sachs, meanwhile, was fumbling through questions on such issues as the Gramm-Rudman deficit reduction legislation, while at the same time trying to figure how to respond to Schaefer's imminent departure.

It was classic Schaefer: Do the unexpected. But the mayor's advantage appeared to evaporate when he packed his briefing books and left.

Suddenly the issue became his leaving, and Sachs' response to it, rather than the substance of the debate. It was as if the Japanese had swooped over Pearl Harbor, scared the bejesus out of everyone and left without dropping their bombs.

Since then, Schaefer has highlighted the debate issue rather than defused it. People are now talking about the candidates' characters and fitness for office, a development that plays directly into Sachs' strategy.

Schaefer, ahead 20 points in the polls, would benefit most from a dull, low-profile, nonconfrontational campaign. Instead, he has people who might otherwise be thinking about their two weeks at Rehoboth thinking hard about the race for governor.

It's a funny way to protect a 20-point lead.