"It would be wrong," says the president in Margaret Truman's new who-dunit, "Murder in the White House," and of course he's right.

It would indeed be wrong for the president of the United States to conceal a confession to murder in the executive mansion and (one is glad to read) this president was not a crook.

The victim of the foul play was the secretary of state. Who well deserved it.

But the whole thing was merely dreamed up by Margaret Truman's fictive imagination:

"I was working on quite a different book," she said over a glass of iced tea while on a visit to the capital a few days ago.

"It was history -- not exactly history -- anyway, I thought 'This is really quite boring to me, so why shouldn't it be boring to readers?' So I just dropped it and suggested a murder mystery instead to my publishers, Arbor House.

"They didn't think it was such a great idea, until I said 'Murder in the White House.'"

And then they perked right up.

"Now, you don't, ah, think a story about murder in the White House is a little like telling them not to put beans up their noses?" she was asked.

"No harm there," she said. "Too much security. There's absolutely no way a stranger could get up to the private quarters."

Of course, needless to say, if the president did in the whole Cabinet even, there'd be no way to keep him from doing it in the White House, security or no security. But in Margaret Truman's book, the president was not the one that done it.

Now 56, Harry Truman's daughter is married to E. Clifton Danile, retired executive of The New York Times and formerly chief of its Washington bureau. Someone asked her how the White House, her old stomping ground, looked and she said mercy, she had not thought to look at it.

Old-timers well know it was her father who stuck on the balcony of the South Portico, to the anguish of all who believe old houses should not be nit-picked at. But in this matter the daughter is fiercely loyal to the father:

"Yes, he added that balcony. And I have never met any member of a president's family since then that was not very grateful. You can sit out there and get the fresh air in real privacy."

She herself has balanced a famous name with a private life. In New York nobody bothers her when she walks down the street unless she's been on television, and then she hears them speculate whether that's little Margaret Truman and the other old lady says no, and the first one says yes -- "and I think it's time for me to move right along."

"Our youngest son -- we have four -- is going off to prep school and I'm getting him ready. We have a triplex apartment, we bought it years ago and you wouldn't believe what we could sell it for now. We really don't need so much space, I suppose, but if we sold it -- "

"Even if they marry," she was warned, "they keep coming on back. The wife will drop in for a day of errands in the city and bring along all the babies and --"

"No she won't, either," said the author. "I'm going to be one of those grandmothers that says, 'I'll come visit you.'"

Her husband -- and here a wee cloud passed over her face, for she is a loyal wife, yet at the same time, well -- "now eats lunch at his club a good bit."

"Mr. Daniel was, ah, home a good bit?" she was asked.

"At first," she said. "A woman marries a man for better for worse, but not for lunch."

She herself long ago gave up her career as a singer and turned to acting. She loves comedy, and her idea of joy is to play in summer and winter stock companies.

"I only sing in the choir in our church," she went on, "at Fire Island in the summer."

"Fire Island? They have churches there?" she was asked.

"Oh, yes," she said, "I sing in the Episcopal church there. In our part of the island you can't live there unless you're married and have children."

"Do the gay activists know about that?" she was asked.

"They have their own places," she said. "It's not the gays, but the singles in two that are mad at us."

She has toured nine cities whooping it up for her book and it really gets you, after a while, you get truly tired.

And leaving Woodies, she said, she managed to step in the world's mother lode of bubble gum, quite ruining her shoes.

"I have two pairs. A fashionable pair and a comfortable pair. This is the comfortable pair."

"Life is too short to wear uncomfortable shoes at any time," a person of virtue said.

"I know," she said, almost with a sign, but also with that resignation appropriate to the human condition, by which one wears what one is jolly well supposed to wear, until bubble gum sets one free. (And almost certainly, inside the blue canvas comfies, wiggling her toes.)