Montgomery County Executive Sidney Kramer said yesterday he will run as a write-in candidate in the November general election, a surprise move already causing chaos among his fellow Democrats.

After his upset in last month's bitter Democratic primary election, Kramer made a series of gracious statements accepting his loss and pledging support for the man who defeated him, veteran County Council member Neal Potter.

But yesterday, Kramer said he had changed his mind because he was inundated with calls from people who didn't vote in the primary and from others who said they had misgivings about having supported Potter.

"All of them feel, for whatever reason, they'd like an opportunity to vote for Sid Kramer," he said. "They have asked me if I would allow my name to be used. I gave it some serious thought and decided I would."

"This is democracy in its purest form . . . to have the voters have a full voice," said Kramer as he announced he would cooperate with a newly organized citizen group spearheading the task of attracting voters for a write-in candidacy.

Potter, who expected to face only Republican Albert Ceccone in the Nov. 6 election, reacted with incredulity yesterday to Kramer's decision to run for a second time.

"I thought he had accepted, in a graceful way that is typical of him, the results of the primary as one is expected to do when one engages in such a primary process," said Potter. "This is an astonishing development."

Kramer's decision, the latest in a series of strange twists in Montgomery County politics this year, caught Democratic Party leaders off guard.

Some leading Democrats said Kramer's bid would be futile -- no write-in candidate has succeeded in recent Montgomery history -- and would serve only to hurt the party while working to the advantage of Republicans. The county GOP, outnumbered in voter registration, has been shut out of local political offices since the 1970s.

County Council member Bruce T. Adams, who had run on Kramer's slate in the primary, said the decision "completely contradicts" everything Kramer said after the primary. "I was impressed with the way he handled himself. I thought it was classy . . . . I am embarrassed for him."

Council President William E. Hanna Jr. said, "I just hate to see it happen. It just hurts me. He is too good a man to take first an upper cut, then a blow to the solar plexus."

Gov. William Donald Schaefer, who was in Montgomery County last night, said, "My view is I have to talk to Sid and see what is going on."

Kramer's announcement came late in the afternoon as an official of a committee calling itself "The Citizens To Write In Sid Kramer" registered with the county Board of Elections. Such a filing is required under election law if a group is to raise money on behalf of a write-in candidate.

The group's chairman is Fran Abrams, a former county employee now active in county day-care issues. She said the group came together because the low turnout in the primary -- 42.9 percent of registered Democrats -- suggested that the results didn't reflect county sentiment as a whole.

She said the group had no money and was composed of civic and school activists. Abrams said no developers or business leaders are involved in the effort. Real estate interests backed Kramer heavily in his primary effort and have remained wary of Potter's positions on growth.

Michael Gildea, newly elected chairman of the county Democratic Party, said a write-in candidacy is an empty political gesture with "no hope of success." He said he tried to discourage Kramer from associating himself with the effort and said he would try strenuously to keep the party united behind Potter.

Elections officials and party regulars said they were not aware of any successful write-in campaign on the local or state level in recent memory. However, never before has a candidate holding an office of Kramer's stature undertaken such a bid.

"These circumstances are a first . . . . It is impossible to predict the outcome," said one Democratic activist.

Kramer's name will not appear on the Montgomery ballot, a computer card on which voters punch a hole next to the names of the candidates they wish to vote for. In write-in cases, voters must write the candidate's name in a prescribed space on the ballot.

Ceccone, the GOP candidate who had been given little chance of defeating the better-known Potter, said Kramer's entry "guarantees a Democratic Party split" that will help him.

Kramer maintained yesterday that he can win and, in a reversal of his and Potter's roles in the primary, declared, "We know it is David against Goliath and there are great odds."

Potter backers last night moved to shore up support, particularly from newly recruited members of the business community.

R. Robert Linowes, a leading real estate lawyer who had supported Kramer in the primary but is now serving on Potter's finance committee, said he would continue to support Potter. "I just don't understand it," he said.