After digging through dresser drawers and cardboard boxes in the back of closets, True Davis finally found his old PT-109 tie clasp last week and shined it up.

The man who had been John F. Kennedy's ambassador to Switzerland wanted his Camelot memento to wear at a $300,000 fund-raiser he was planning here for Sen. Edward M. (Ted) Kennedy next month.

Davis, former president of the National Bank of Washington and now an adviser to foreign bankers, had put together a list of 300 wealthy "old-line Democrats" like himself who has "not been needed" by the Carter administration and "whose advice had not been sought" during the past three years.

Davis had lined up professional fund-raiser Nancy Cole to run his party, with all the paper work and telephoned follow-ups involved.

Then Tom Quinn, of the Kennedy finance committee, sent word that someone else had already volunteered to stage a $1,000-per-person party here on Dec. 16.

Ethel Kennedy will open Hickory Hill that night for celebrities flying in from all over the country. Even if she can accommondate only 250 in her house, the campaign may come out ahead. Unlike Cole, Ethel doesn't charge a percentage.

The fund-raising potential of the Kennedy sisters and sisters-in-law is something that infuriates the Carter forces, but that is not the kind of thing they can complain about to the Federal Election Commission. At Pat Lawford's last week, her friends gave Ted Kennedy pledges totaling $150,000. l

A finance committee spokesman said yesterday that the clamor of people willing to pay $1,000 for Ethel's party may force them to move the party from her McLean estate to a downtown hotel.

David Eisenhower, finishing a book on his grandfather for Random House, told one of his editors recently that all his research has convinced him there was never a romance between Dwight D. Eisenhower and his wartime aide, Kay Summersby.

David maintains that Ike never loved "anyone" but his wife, Mamie, who died yesterday. "Ike LIKED women, really liked them" he says.

"That gave a lot of people the wrong idea.He was flirting with the nurses at Walter Reed Hospital the day before he died."

Although David has been determined to set the record straight about the Summersby affair, he says his grandmother never really cared what people chose to believe.

Out in Nebraska, where Billy Carter is being paid $2,500 to appear at an alcohol abuse seminar, there was a state of panic when someone in the federal bureaucracy pushed an alarm button from Washington.

Statewide, the program receives nearly $1 million annually from the National Institute on Alcohol Abuse and Alcoholism. Included this year was a special request for $1,400 for the seminar on which Billy will appear.

Dr. William Ford, director of the Nebraska state alcohol program, was told sternly by an NIAAA official that no federal money could be paid to Billy. The $1,400 will pay for a newspaper ad. Billy will be paid out of money raised from ticket sales and contributions from local businessmen.

Fifteen runners who plan to compete in the Marine Corps Marathon here on Sunday -- many of them doctors -- have made reservations at Petitto's for tomorrow night, to stoke up on the carbohydrates in homemade fettuccine and lasagna before all that exertion . . .

When Evelyn Lincoln wrote her first book about the years she worked as JFK's secretary, she kept it so secret that Bobby Kennedy, didn't know anything about it until he got an invitation to her publisher's party. Now she's writing a novel. The first anyone knew was when a Kennedy staffer overheard her telling someone about it in a rstaurant recently. But no one can find out what it's about. Asked point-blank, she refuses to tell . . .

New York photographer Ken Regan, whose credit line appears all over the newsstands currently because he is the Kennedy family's favorite, probably isn't going to take financial advantage of his inside track. He would rather produce movies, he says, and has one underway in London.