A majority of D.C. Council members have signed a letter endorsing Hilda H.M. Mason's bid to keep her at-large council seat, a move that some said they made to derail Mayor Marion Barry's attempt to join their ranks.

The letter, which has not been released publicly, had been signed by eight council members as of late yesterday and several more were expected to sign today, according to members. Mason's Statehood Party campaign, which many political observers say is most vulnerable to Barry's candidacy, would not comment on the endorsements.

The council's effort to rally behind Mason comes three weeks before the Nov. 6 general election, and just as Barry's campaign for one of the two at-large seats on the ballot has intensified. It also is the first indication of an active effort by Democrats to try to stop Barry, who abandoned the party this summer in his move to remain in politics.

"Most of us are very uncomfortable" with Barry's campaign, said council member Frank Smith Jr. (D-Ward 1). "All along I've said I don't think the mayor should be on the council."

Council member Jim Nathanson (D-Ward 3) said his signature on the letter is intended to lure voters away from Barry -- and from other candidates who could help his cause by splitting the vote.

"One of my priorities in this election is not to have Marion Barry elected in this government," Nathanson said. "This gives the community a direction to go so as not to split the vote."

Barry campaign manager Anita Bonds sought to play down the importance of the group endorsement, saying, "When elected officials make an endorsement, a declaration of support for a colleague, it doesn't always translate into votes. I've not known it to stimulate the voter."

Barry announced while awaiting trial on federal drug and perjury charges that he would not seek a fourth term as mayor.

Shortly after he was convicted in August of a single count of cocaine possession, Barry switched his voter registration from Democrat to independent and petitioned to appear on the general election ballot as a candidate for an at-large council seat.

Mason, 75, is a three-term council member who is battling a crowded field of candidates to keep her job.

The top two vote-getters in the race will win the seats. School board member Linda W. Cropp easily won the Democratic nomination for an at-large seat last month. More than 70 percent of the city's registered voters are Democrats, which gives Cropp a substantial edge in seeking one of the seats.

Thus, many see the race for the second seat as among Mason, Barry, Republican W. Cardell Shelton and four other independents: Ray Browne, Jim Harvey, Clarene Martin and R. Rochelle Burns. A divided vote, several council members said , likely would mean a Barry win.

"This is a race between Hilda and Marion," Smith said.

Yet in recent weeks, there have been signs that Mason's campaign was struggling. She has reported raising about $70,000 -- but nearly all of it has come from personal loans she made to the campaign.

Council members said they hoped their letter of support for Mason would boost her standing in the community.

"Hilda is a wonderful lady who has worked very hard on social issues," said council member H.R. Crawford (D-Ward 7), a longtime ally of Barry's who signed the letter. "She's very sincere and devoted."

Council member William Lightfoot (I-At Large), who once supported Harvey, said he now believes that Cropp and Mason are the voters' best choices. "I don't think Jim is a viable candidate now, so I went to Hilda," he said.

Other council members who have signed the letter endorsing Mason, according to a source in the Mason campaign, include Democrats: Council Chairman David A. Clarke, John Wilson (Ward 2), Harry Thomas Sr. (Ward 5), and Nadine P. Winter (Ward 6). Clarke said he is also backing Cropp.

Council member Wilhelmina J. Rolark (D-Ward 8) also is endorsing Mason, she said last night.

Rolark, like Clarke and Thomas, indicated that she considered herself as supporting Mason rather than repudiating Barry.

Winter and Wilson could not be reached for comment last night.

Barry, who is scheduled to be sentenced in U.S. District Court shortly before the election, has stepped up his campaign in recent weeks. He has raised about $35,000, begun participating in candidate forums, and is preparing to mail pamphlets promoting his candidacy to about 60,000 District voters.

But several council members said yesterday they intend to reinforce their endorsement letter by actively campaigning for Mason. "The only way for the mayor to get to the council is for the vote to be fractured," Nathanson said. "We can't allow that to happen. The city has to cleanse itself morally and ethically so we can move on."

Staff writer Ruben Castaneda contributed to this report.