Former Arizona governor Bruce Babbitt, perhaps the darkest horse among Democrats running for president, is to participate tonight in a nationally televised expose of his secret character flaw.

Unlike the cases of other candidates whose ethics have been questioned this year, Babbitt hopes his expose will help his campaign: It is a "Saturday Night Live" skit in which he is ambushed with an "attack video" conclusively proving his perfidy. He tried to sneak 14 items through a 10-items-or-less supermarket checkout line.

For Babbitt, who is stuck near the bottom of the polls and woefully short of funds, it could be a golden opportunity to reach millions of people and give his campaign a boost. Or it may turn out to be a major mistake. He taped his performance Thursday in New York.

Roger Ailes, Vice President Bush's media consultant, thinks that the performance is a reasonable move. "If I had Babbitt's numbers in the polls, I'd do 'Saturday Night Live,' too," Ailes said. "I'd do the Thanksgiving Day Parade as one of the balloons if they wanted me to. It's the old joke -- you can't get killed jumping out of a basement."

"Look, I don't think anybody is going to detect a prairie fire of support as a result of an appearance on 'Saturday Night Live,' " Babbitt said yesterday. "But a little exposure is always helpful, no doubt about that. Humor, in its best form, does have a humanizing effect."

Babbitt is so far the only taker among a dozen Democratic and Republican candidates invited to appear on the NBC show.

Babbitt admitted that he had initial misgivings. "Originally, I had been inclined not to do it," he said. "I sort of had visions of pie-throwing, slapstick sort of stuff." He said he changed his mind after reading the text and the deal was clinched when Babbitt's 12-year-old son, Christopher, demanded that he go on.

"It's a funny show," said Babbitt strategist John Russonello. "It will let people see a side of Babbitt that they haven't been able to see enough of in the course of the debates. The debates have shown the very serious and articulate thinker. But there's another side of him that loves jokes and loves to play jokes, that loves to laugh at himself."

"Our primary audience happens to be Iowa caucus attendees," said Babbitt press secretary Mike McCurry, "and many of them are somewhat aging Baby Boomers who like the idea of staying up late to watch 'Saturday Night Live' even if they don't actually watch it. . . . The best thing that could happen is that a couple of people who may have thought Babbitt too cerebral or too stuffy to be president would take another look at the guy."

Babbitt has a television style that a consultant to a rival campaign describes as "a cross between Jimmy Stewart and Richard Nixon." His first performance in a television debate, in Iowa, was uniformly deemed less than successful.

In appearing on "Saturday Night Live," Babbitt follows such politicians as former president Gerald R. Ford, third-party 1980 presidential candidate John Anderson and, after his campaign ended in 1984, Jesse L. Jackson.

Some people are skeptical. "This sounds like a guy who's decided he's going to have a new profession come February," said Bush press secretary Peter Teeley.