About the time John Stockton was hitting his blindfolded, behind-the-back, twisting, turning, spinning, no-way jump shot to beat the third quarter buzzer by a thousandth of a second and give the Jazz an 81-69 lead that should have been 78-69, a fan in the expensive seats pulled out a cardboard poster he had heretofore seen fit not to make public.

"UTAH JAZZ CAN DO IT: 1988 WORLD CHAMPIONS!"Honest.

Such has the series turned as the Jazz and the Los Angeles Lakers decide who moves on to the Western Conference finals. Forget that another 7-game series to decide the conference title would come next, followed by a Championship Series versus the Eastern Conference winner. Forget that there's yet another game Sunday. The Lakers are the defending world champions, and if they can fade like yesterday's news in the Salt Palace - by a 96-89 count last night - make way for fantasies and other notions.

The Jazz own this town. Till Sunday anyway. As memorable nights in the Salt Palace go, last night topped every previous basketball night and/or rock band performance. Combined. At times it was difficult to tell the difference.

"The Salt Palace will be rockin'," Jazz forward Karl Malone had predicted when the series shifted from Los Angeles. He was right. There hadn't been a tougher ticket on West Temple since, well, since never, and certainly not as much noise. Everybody wanted to be seen and heard. This included several Los Angeles Lakers fans who normally don't get excited about traveling until Boston enters the itinerary.

But this was a rare thing - a 1-1 series in the early rounds - and for last night's game a number of the $100 courtside seats were filled by Lakers fans. Fifteen of the seats had been purchased by Jack Nicholson, the quintessential, actor-type, shades-wearing, Laker fan who didn't himself make an appearance but presumably sent his emissaries.

"The thing about the L. A. people," said Jazz president Dave Checketts, "is they called and asked for seats and complained that the prices were too low. The $100 seats were the best we could do for them, the ones we usually save for when Robert Redford calls. They grabbed all they could."

Still, they were handily outnumbered by Jazz fans, who wore dark glasses that had been handed to them before the game by Jazz management. The Jazz distributed the shades to courtside customers in an effort to make the Lakers and their fans feel cool and right at home.

The homemade sign hung conspicuously directly across from the Laker bench didn't have the same intent, however.

"If Superstition Doesn't Get Ya, The Altitude Will," said the sign, referring, respectively, to Friday the 13th and 4,500 feet above sea level.

There was also a lazer show - a good fireproof way to dazzle a crowd for a thousand bucks - and if the mood wasn't hardrock before the lazers helped introduce the Jazz players, it was afterward. Ear doctors were passing out their cards.

If the Jazz have had their troubles in the past, this was a payback. People were wearing purple, gold and green warpaint. They stood most of the game, waving purple, gold and green placards. At the end of a 31-23 first quarter they were warmed up and the double question was how long could the Jazz keep out-scoring the defending world champions - since last Sunday it was now seven straight quarters - and how long can vocal chords last?

By the stretch run of the fourth quarter, when the P. A. system went momentarily down and when the Jazz went over four minutes without a basket to let the Lakers creep back within four points, the double answer appeared to be "not long enough."

Nobody was wearing shades anymore. It wasn't cool to be cool.

Then the microphone came back to life and Malone and John Stockton and Mark Eaton went back to work, doing improbable things mostly when they were off-balance, and it was all over but the shouting and the placard waving and the lining up at the ticket office for playoff tickets to future series.

Better to be safe than sorry. In this business there's only one true axiom: You're only as great as your last win.