Officially, the American Bar Association never heard of it because there is no such group. Unofficially, the White Collar Criminal Bar really does exist -- or coexist.

It's composed of both prosecutors and defense lawyers, and they're getting together for the first time Saturday night, thanks to Washington attorney Richard W. Beckler, who has known them all for years.

"Sometimes I've been been on cases with them, sometimes on cases against them," Beckler said yesterday of the 125 guests he's invited to a black-tie dinner. "I've been wanting to get them together for a long time."

They include such legal eagles as William G. Hundley, who represented former attorney general John Mitchell in the Watergate coverup trial, and Earl J. Silbert, the then assistant U.S. attorney who tried the first Watergate case.

Others are of more recent fame, including Richard Janus, who represented arms merchant Albert Hakim, and Plato Cacheris, who represented Fawn Hall in last summer's Iran-contra hearings. Beckler himself is defense attorney for former national security adviser John M. Poindexter.

Like everyone else, Beckler is waiting for independent counsel Lawrence E. Walsh to complete his yearlong criminal inquiry into the Iran-contra affair, in which wide-ranging indictments are expected. Yesterday Beckler said he expects Walsh to take action by the end of March.

That possibility has nothing to do with why he's giving the party, Beckler said, which should come as relief to Poindexter since the party is -- quoting from Beckler's invitation -- "In Memory of the St. Valentine's Day Massacre."

Patti Davis' second novel is scheduled for publication sometime next winter, though no one yet knows whether it will make it into the bookstores before Dad leaves the White House. Unlike her first novel, "Home Front," which Crown also published, she is writing this book by herself. In initial discussions with her publishers she talked about a story of political intrigue along the lines of "Day of the Jackal."

"Home Front" was the semiautobiographical account of a rebellious daughter of a California governor who became president. No word on whether this one will have characters with any similarities to persons living or dead.

Pete Roussel, former deputy press secretary to President Reagan, is back in town after a year's hibernation in Texas, where, among other projects, he was working on a novel with a White House setting. In Washington, he plans to enter the public relations field and also update a George Bush biography that E.P. Dutton bought in 1980, then shelved when Bush failed to win the GOP nomination for president.

He first saw her on television, standing on the platform with her father at the 1984 Democratic National Convention in San Francisco. But not until Chicago Bear Keith Van Horne heard Eleanor Mondale in a guest host slot on Chicago's WCKG-FM radio a couple of years later did he try to get acquainted.

"I want to meet Eleanor Mondale. Ask her if she wants to meet a Chicago Bear," Van Horne told the station manager, with whom he worked on a weekly radio report about the Bears.

This story might have ended right there. Eleanor sent back word that she didn't want to meet Van Horne, who plays offensive right tackle -- or any other Bear either, for that matter. Van Horne persevered, however. They met, she reconsidered, and last month, on Eleanor's 28th birthday, he popped the question.

Her reply casts former vice president Walter Mondale as father of the bride in an April wedding in Hudson, Wis., where the Rev. John Maxwell Adams, a retired Presbyterian minister and father of Joan Mondale, will officiate, assisted by Walter Mondale's brother, the Rev. Lester Mondale, a retired Unitarian minister.

Another Mondale wedding coming up, in June, will be Theodore (Teddy) Mondale's to Pam Burris of St. Paul. When Teddy, 30, isn't studying for his law degree at William Mitchell College in St. Paul, he is campaigning in Iowa for Massachusetts Gov. Michael Dukakis.

Eleanor's interest in politics currently is confined to a book about presidential children, which she's writing with Chicago free-lance writer Magda Krantz, and which may yet turn into a broader study of political children.

Walter Mondale, who also is sitting out this part of the campaign, is expected to go on the hustings once the Democrats choose their candidate in July. After the election, Joan Mondale says he'll decide what he wants to do about running for the Senate in 1990. Meanwhile, he and Joan have agreed to dog-sit while their son and daughter are off on their respective honeymoons.

"I don't have any grandchildren," Joan said yesterday, "but I've got some grand dogs."

Nancy Reagan will become the first first lady in Boy Scout history to receive its Buffalo Award when the scouts present their annual report to President Reagan today in the Oval Office.

Being recognized for her work in combating drug and alcohol abuse, Mrs. Reagan is one of only a handful of women so honored by the scouts. Others have included Girl Scouts President Betty Pilsbury in 1986 and Ann Nally of Annandale, community servant, parent and dedicated scouter, in 1982 -- the year President Reagan was also a recipient.