First came Hogan and his aides-de-camp, eight of them in all; some with notebooks in hand, others with packets of newspaper clippings. They trooped directly upstairs to a conference room, closed the door, and spent the next hour refining their strategy and going over the tough questions.

Then came Kelly and two of his loyal assistants. One was holding an oversized piece of construction paper on which was drawn a color-coded budget chart. It was Kelly's security blanket, faded and worn after four years of use.

For months, Republican Lawrence. J. Hogan and Democrat Winfield M. Kelly Jr. had been arguing over surpluses and taxes, opinion polls and campaign finances, sunroofs and car radios. Until now, however, they had been like badminton contestants playing at different locations, with one, then the other, lobbing a shuttlecock over the net to an empty court.

That would change on this Tuesday night at a WJLA-TV studio in Washington. Here, finally, the two candidates for country executive in Prince George's County would be in the same room at the same time to talk about the same thing.

It was the night of the debate.

Before it started, the politicans huddled in a waiting room with the moderator, Paul Barry. He asked if Kelly or Hogan had any predebate questions. Hogan had one.

"Is it all right," asked the 50- year-old former FBI agent and three term congressman, "if I call Winnie a no-good, dirty liar?"

Hogan debate began amicably enough with Hogan saying that if the people are happy with the way Prince George's has been run and are not unhappy with paying high taxes they should vote for Kelly, and Kelly responding that when he took over as county executive four years ago "Prince George's was last in about everything but taxes."

Hogan aides Lewis Helm and Ted Cormaney, watching the taping in a nearby viewing room, seemed more excited by the camera angles than the statements. Hogan, sporting contact lenses, spoke directly into the camera, while Kelly appeared to be addressing himself to some unknown object in the back of the room.

"He's looking at the questioner, I think," said a red-faced John Lally, Kelly's top aide, who may have been still upset that the station personel would not let Kelly take the color-coded chart into the studio.

Even the first question from reporter John Harter found Kelly and Hogan in a friendly mood. The question was why Kelly, with all the advantages of the incumbency, was shown to be the underdog in all the polls.

Kelly said he was trailing because Hogan's popularity as a congressman "mystically carries over even today" whereas he was burdened with a job that carries "a bit of negativism with it."

Hogan said he mostly agreed with that assessment, and that Kelly had he difficult job - problems are complex."

From there, however, the debate turned to the issue of taxes, and the name-calling began, or at least the first-name-calling. For several minutes, Kelly began nearly every statement by saying "Larry, that's just not true," and Hogan began nearly every statement by saying "Winnie, that's not true at all."

Hogan had an inherent advantage in the first-name-calling, since there is only so much one can do with the name "Larry," while "Winnie," when uttered properly, can sound like a slur. Hogan did his best to make "Winnie" sound like "ninny." Kelly showed more respect for the name "Larry," perhaps because that was the stage name he used years ago when he was a teen-age song-and-dance man in Brentwood.

Although Kelly was not allowed to display his budget chart - which graphically shows how much less the yearly budget increases have been since he replaced Republican County Executive William Gullett in 1974 - Hogan was able to take full advantage of the materials he carried into the studio.

At one point, he pulled out a piece of paper and began reading off all the different taxes - 16 in all; ranging from boat slip taxes to telephone taxes to apartment taxes - that Kelly had proposed since he took office. The camera peered over Hogan's shoulder and focused on the list as Hogan spoke.

Helm and Cormaney, two middle aged, conservative-looking man, slapped hands as they watched this from the viewing room.

Kelly, undaunted, replied: "Larry knows full well that every tax that was considered was a move away from the property tax, which is the major burden for the people of Prince George's." He noted that in 1978 the average county homeowner received a $100 tax cut, the largest in county history.

The debate ended before Kelly and Hogan could talk about anything but taxes. It will be aired at 7 p.m. this Sunday when the competition will be "60 minutes" and Walt Disney. Then it will be reshown at 6:30 Tuesday morning when there will be even tougher competition: sleep.