Montgomery County Council member David L. Scull set the stage yesterday for a political contest with fellow Democrat Sidney Kramer by announcing he wants to run for county executive in 1986.

"I lean towards running," Scull said in a lengthy statement that was phrased like a campaign manifesto, but which he insisted was not. Scull stopped short of formally declaring his candidacy for the county government's top job, saying any such announcement would come later this year.

However, Montgomery Democratic leaders are interpreting Scull's statement as a clear indication that he has decided to challenge Kramer in the party's September 1986 primary. County Executive Charles W. Gilchrist announced last year that he will leave politics at the end of his second term to study for the Episcopal priesthood.

"I'm convinced he's running," said Jay S. Bernstein, the county Democratic Party chairman. "He wouldn't have released this statement today if he weren't running."

"My instincts tell me he's running," said County Council member Rose Crenca, another Democrat who has tangled publicly with Scull on a variety of issues.

Before issuing his statement to reporters, Scull consulted with Bernstein and all six of his council colleagues. Bernstein quoted Scull as saying that a recent private poll showed Scull leading Kramer in name recognition among voters.

Scull, the 42-year-old millionaire heir to one of Montgomery's oldest financial and political fortunes, would be a formidable opponent for Kramer, also a wealthy businessman, who is head of Montgomery's State Senate delegation.

Kramer has been working for months on the premise that Scull will be his chief rival for the county executive's job. He already has hired some campaign staff, held fund-raisers and has quietly consulted with Democratic precinct officials about the campaign.

Similarly, Scull -- who was poised to challenge Gilchrist in 1982 but backed out of a campaign at the last minute -- also has discreetly sounded out Democrats about his bid for higher office.

By announcing his desire to run, "he wants the world to say, 'Oh, isn't that great?' or 'Are you out of your mind?' " Crenca said. "He's politically astute. He wants to hear the reaction."

To speed that reaction along, Scull recently sent letters to one-third of the Democrats' 400 precinct officials expressing in general terms his desire to meet with them about Montgomery political issues.

"The only thing that will change his mind right now are elected officials and precinct workers," Bernstein said. "But at this moment, you can safely assume David is a candidate."