Key precincts on the West Coast had yet to report, but sources within the Big Boy campaign said last night that the mascot of Marriott Corp.'s restaurant chain appears to have survived a vote to eliminate the chubby cherub.

"The indications are it looks pretty good for the guy," a campaign official said, adding, "He's doing a little bit better than I thought."

Neither Big Boy nor his campaign manager, Speedy Alka-Seltzer, could be reached for comment.

The effect of the apparent landslide victory on the 1986 national congressional elections and the 1988 presidential race could not be assessed immediately.

Marriott has scheduled a press conference for today to announce the results of the voting, which has been going on for five months. "Should he stay or go?" the company asked customers of the pompadoured, checkerboard-clad corporate symbol, who stands enshrined in plastic outside most of the nation's 800-plus Big Boy restaurants.

Early ads featured a "Mr. Big" who demanded that Big Boy be fired. Big could not be reached for comment yesterday, though Marriott officials said he would attend the press conference.

But Big's demand apparently crumpled in the state of public support. In the grand Chicago tradition, Big Boy customers apparently voted early and very often -- it appeared that the election drew several hundred thousand votes. Big Boy's cause was no doubt helped by impassioned pleas made in television commercials on his behalf by the Michelin Tire Man and Dutch Boy paints mascot. Tony the Tiger, however, remained neutral in the election, refusing to pronounce his fellow advertising symbol "Grrrrrrrreat!."

Marriott officials insisted that they would abide by the public's vote -- the Big Boy chain may stuff potatos, but not ballot boxes, according to Vincent J. Webb, national marketing director of Big Boy restaurants. "Whatever happened, happened," Webb said.

But despite hopes in some quarters for a Truman-like upset of the mascot, Big Boy apparently prevailed. In Indiana, for instance, one of the vote states where early returns were in last night, the vote was a landslide: 40,000 for the Big Boy, 7,000 against. "But the Hoosiers, they're a conservative lot," said a nervous campaign staffer.

Still, analysts said it appeared that there would be no late-night surprises in the balloting. "Thomas Dewey does not win," said one source familiar with the tally. Big Boy was also believed to have carried the Washington area, crossing party and state lines to do so.

California was considered the most important state for the candidate, as the birthplace of Big Boy and the state most populated by the restaurants bearing his name. But sources said straw polls indicated a heavy favorite-son turnout appeared to be carrying the election for him there.

Webb said Marriott was a little concerned about vote-fixing in some areas, particularly college towns. "We kept waiting for a college fraternity to come in with 200,000 ballots or something, but it never happened," he said.

Big Boy's handlers said they hoped the favorable returns would allow the candidate to get a good night's sleep to prepare him for the press conference. "If I were Big Boy and I were pacing in some kind of locker room waiting for my public appearance tomorrow, I wouldn't sweat much," said a campaign official.

"We'll see what happens to the little guy," Webb said. "Speedy's with him, and they'll pull him through the night."