What a difference incumbency makes. Four years ago, when he was locked in a three-way race for the Democratic nomination for Montgomery County executive, Charles W. Gilchrist operated on a tight schedule, anxiously racing from endorsement announcement to kaffeeklatsch in search of votes.

Yesterday, at a scheduled 8:30 breakfast meeting and press conference where Montgomery County AFL-CIO leaders were to announce their support for Gilchrist, the food was almost an hour late in arriving, only one reporter showed up and Gilchrist and two staff aides were left standing in the hallway at the Silver Spring Armory until someone came to open the door.

Gilchrist was Mr. Cool. Facing only a largely unknown and underfunded opponent, Wade Dunn, in the Sept. 14 primary, the delay was no problem, given the laid-back, leisurely pace of his reelection campaign.

In 1978, such a scenario would have caused havoc with a packed schedule of politicking.

"No question, you sleep a lot easier, you read the papers a little bit more dispassionately," said Gilchrist's special assistant, Edmond F. Rovner. " But you've got to do the same things, and attend the same functions, because you can't afford not to."

Gilchrist's campaign staff has not had a meeting for about three weeks, said chairman Gilbert Lessenco, and Gilchrist does not plan to open a campaign headquarters for another week. Asked if he didn't have anything to do, Lessenco replied, "Well, I guess that's true."

The most serious of Gilchrist's potential primary opponents, council member David Scull, bowed out in February, and reaffirmed that decision last week by filing for an at-large council seat.

The Republicans are locked in a three-way battle for the executive's nomination, diverting their time from attacking Gilchrist to attacking each other.

The Gilchrist campaign has hired a public relations adviser, Ron Mitchell, whose first product is a slick blue-and-white brochure full of Gilchrist pictures and emphasizing his favorite issues -- drunk driving, crime, senior citizens, jobs and the county budget.

The campaign also has taken out a full-page advertisement in a county newspaper, listing the names of more than 300 supporters.