The first political struggle among the all-Democratic membership of the Prince George's County Council over the election of a council chairman in five years has been settled in favor of Councilman William B. Amonett, several council members said yesterday.

Councilman Gerard T. McDonough, the leading council spokesman for outgoing Executive Winfield M. Kelly Jr. and Amonett unofficial campaign manager, said he had been promised the six votes necessary to elect Amonett over Councilman Parris N. Glendening.

Glendening acknowledged that Amonett appeared to have the necessary votes, but charged that McDonough had obtained the key vote of incoming Councilwoman Deborah R. Marshall in exchange for a promise that Marshall would become council vice chairman.

"Several scenarios were discussed, (at a meeting last Wednesday) and one of them included Debbie as vice chairman this year," McDonough said, "but that's not going to happen." Councilman David G. Hartlove, McDonough said, was the choice of the coalition supporting Amonett for vice chairman.

The chairmanship election - which will not take place until the council's Dec. 5 meeting - has been the center of a daily-changing political climate of vote-switching, backbiting and backroom negotiation since the Nov. 7 election, and Glendening pointed out yesterday that it might not yet be over.

"The vote has been flowing back and forth constantly," Glendening said. "Several people have been wavering and may still switch around."

The chairmanship struggle first burst into the open on Nov. 14. When Francis B. Francois, then considered the most likely candidate to succeed retiring council chairman Francis W. White, sent a memo to the other ten members of the council announcing he did not want the job and would support Amonett.

It soon became evident that Amonett had four solid votes for the chairmanship - his own and that of council members Hartlove, McDonough and Francois.

Glendening, by contrast, appeared to have three solid votes - his own and that of councilmembers Frank Casula and Ann Lombardi.

Incoming Councilwoman Sue V. Mills, angered over the "low politics" of the Francois memo, said she decided to vote for Glendening as a direct result of Francois' action.

Meanwhile, Councilwoman Sarah Ada Koonce announced that she would not support either Glendening or Amonett until the chairmanship had been determined.

That left Floyd E. Wilson Jr. and Marshall, as the swing votes.

MnDonough said that Wilson and Marshall had met with him on Wednesday and had said they would vote for Amonett.

Last nigh, Amonett, too, was confident. As far as I can tell, I have the support (for the chairmanship)," he said.

"I think my experience was attractive," Amonett said. "I'm older than some of the others." Amonett is 47; Glendening is 36.

Amonett is beginning his third term on the council, and was chairman two years ago under Kelly. He has been aggressive in cutting back on county costs, and is currently sponsoring a resolution that would require all county departments to submit cost-cutting plans.

The resolution also asks incoming Republican Executive Lawence Hogan to find ways to cut personnel and purchasing costs. But the resolution, Amonett said, is not a challenge to Hogan.

"Having a Republican as executive will make a difference in the basic suspicions of the council and executive towards each other," Amonett said. "But if it's up to me I'm sure (Hogan and I) will get along."

The council chairman has few specific powers under the county charter, but receives a salary bonus of $2,500 annually and is usually more visible than other council members.

Glendening, who is entering his second term as as a council member, has been aggressive in backing legislation limiting billboards in the county and regulating cemeteries.

In addition, the post has assumed more importance this year because Kelly's defeat has left the Prince George's Democratic party without an obvious leader.