For some it may be the optimal pairing of folks one loves to hate. For others it is simply a situation ripe with lip-smacking possibilities. For nearly everyone, tonight's scheduled bout between Richard M. Nixon and Barbara Walters has to be considered the ultimate TV game show.

The Walters interview with the former president, to be done live in New York, will take up the entire hour of ABC's magazine show "20/20" on Channel 7 at 10. Whether or not fur flies, danders rise and sparks spark, this promises to be a tango so tangy that its news value becomes peripheral.

Walters, confidante of kings and chorines, who tippytoed into the shah's sickroom and went to the mountain-top with Fidel Castro, is TV's foremost interviewer, and she is looking forward to going a few rounds with a man who had been up to now one of TV's least eligible interviewees.

"We've been trying to do an interview with Richard Nixon for seven years," said Walters late last week from her New York office. "We sent them letter after letter. And then recently they called and asked if we were still interested. I said yes, we were."

However, the possibility has arisen that Walters may be too interested -- so much so that she and ABC News have made concessions to the Nixon camp about what will or won't be asked. Because the Nixon people made too many demands, Don Hewitt, executive producer of the CBS News magazine "60 Minutes," told them to go peddle their papers and, as with G. Gordon Liddy and his recent book whirl, ABC got Nixon as a hand-me-down.

"I really don't know what Don Hewitt's experience are," Walters says. "As far as we're concerned, there are no ground rules. They said they would prefer to do it live. Well, we liked the idea of doing it live. There's that sense of spontaneity -- people at home saying 'What will she ask next?' -- and always those last-minute questions you can ask about something that happened that day.

"So I talked with Roone (Arledge, president of ABC News) and he said 'Fine.' Roone just loves live interviews. But there was no discussion with Nixon's people of what would be in or out."

Walters concedes, however, that she is not likely to ask a lot of Watergate questions. "There are a few new questions about Watergate that have come up in the last few months which I might want to ask, but I don't want to rehash what David Frost spent 45 hours talking to Nixon about," she says, referring to Frost's syndicated 1977 Nixon interviews.

According to Hewitt, however, Nixon came this time with strings attached. It all began, he says, when CBS News President William Leonard ran into former Nixon press secretary Ron Ziegler and Ziegler suggested a rematch on "60 Minutes" between Nixon and Dan Rather, who'd irked Nixon with alleged impertinence prior to Nixon's resignation and discussions of his mother's fitness as a saint.

"It sounded pretty good to me," says Hewitt now, "but then Ziegler said we couldn't talk about anything that happened before Nixon left the White House. He said to me, quote, 'I don't want any questions like, "Why didn't you burn the tapes?"' I said nothing doing, but he said to talk to Jack Brennan, an aide to Nixon."

To Brennan, Hewitt suggested the date of May 4 for broadcast of the interview and according to Hewitt, Brennan said "Great -- the books'll be in the bookstores by then," referring to Nixon's newly published tome on foreign affairs.

Hewitt also says Brennan wanted the subject matter limited to foreign policy and, when that suggestion was rebuffed, then insisted that the interview cover only "the present and the future." But Hewitt was equally piqued at the primary stipulation, that the interview be done live so it couldn't be edited down later for broadcast.

"I know why they wanted it live," says Hewitt. "At least I can guess. Because, remember that brouhaha when Rather was allegedly rude to the president during a press conference? Well, there is no way Rather could interrupt Nixon if it was live withoug appearing to be rude. I think that's what the Nixon people thought."

Walters says she doesn't think it's an imposition to do the interview live. "A growing number of people do not want to be interviewed unless it's live and unedited," she says. Israeli Prime Minister Menachem Begin, according to Walters, will only be interviewed on tape "to time," meaning for the amount of time the interview will actually be on the air.

And presidential adviser Zbigniew Brzezinski will ask her "How much are you going to use on the air?" and if she says "Five minutes," he'll say, "Fine, I'll give you seven," to minimize the amount of material that can be cut out.

"I wish you would just ask Barbara one question," Hewitt says. "Ask her whether, all things being equal, she wouldn't much rather do the thing on tape and then edit it later."

Walters says, "I've done interviews both live and on tape, and it's harder on the reporter to do it live. '60 Minutes' only does edited interviews, and so there the reporter always has the advantage."

Hewitt says, "When it's live, you can't concentrate on content. You have to split your attention between content and the clock. Also, when you tell someone you will put them on live and promise not to edit it, it's like publishing your notes. In effect you are letting them use your air to make a speech."

Walters says she does gey "butterflies" a bit about going on live and that viewers may have to put up with a little "long-windedness" that might be edited out of a taped interview, but she also says she has no qualms about interrupting Nixon, even though when she interrupted Begin on a recent "Issues and Answers" he snapped, "Don't interrupt me, Barbara."

There is no clause that says she has to ask Nixon about his book, Walters says. "I'm free to ask any kind of questions I want." And Nixon is taking some risk by going on live, too, she says; "If he perspires, then he's going to perspire."

Walters says Nixon is Nixon and this is only his second major TV interview since leaving the White House.

"Whenever you mention Richard Nixon, you hear, 'Aha! Are they ever being used!'" says Walters. "I'm not being used. I want to interview Richard Nixon. Everyone wants to interview Richard Nixon. Richard Nixon's views are news, so I don't think we're being used at all."

Of her interviewing technique, Walters says, "I want to be tough but fair.

I could be sensational. Some people are saying I should make him squirm, and other people say, 'Why give this man air time?' and all of that."

Walters is asked, though, if she is intimidated or scared by the prospect of facing Nixon live on the air.Barbara Walters scared or in awe? "No, I don't think so," she says. "No. Not of anyone."