The Republican National Convention should help George Bush cut into Michael Dukakis' advantage in the public opinion polls if historical trends hold up, political analysts say.

Several national political pollsters said they expected Dukakis would enjoy a surge in the polls coming out of the Democratic National Convention, and they said that would be in keeping with past post-convention poll trends.But these experts also said that because of this tendency for candidates to get a public opinion lift from all of the exposure, Bush should be able to use the GOP extravaganza in New Orleans Aug. 15-18 to help his standing.

While Bush could take some solace from such a boost, analysts noted that history often has shown these post-convention spurts to be short-lived.

For the moment, Dukakis has a commanding lead. He was ahead by 17 percentage points in two polls last week, 18 points in two others. Survey results just before the July 18-22 convention had ranged from a dead heat to a slim Dukakis lead.

But what would have been a remarkable surge any other week was routine by post-convention standards. Conventions traditionally boost the nominee by 10 or more points, mainly because of the intense positive exposure they provide.

"The bounce Dukakis got seems to be pretty typical of what we've seen in the past three elections," said Larry Hugick, political poll chief for the Gallup Organization.

"The polls are accurate. The question is, are they predictive of what will happen on election day," said Harrison Hickman, a Democratic pollster. "There is no question that the race will tighten up."

If getting the bounce is easy, keeping it is not. Gallup polls in recent elections showed convention surges settling as the campaigns progressed and voters began paying more attention to the issues:

-Jimmy Carter went from a 17-percentage-point lead over President Ford before the 1976 Democratic convention to a 33-point lead after it. But within a month his lead was down to 13 points, and he won in November by just 2.1 points.

-In 1980, Ronald Reagan went from a 3-point lead over Carter before the Republican convention to a 16-point lead after it. A month later it was a tie, though Reagan went on to win by 9.7 percentage points.

-In 1984, Walter Mondale moved up from a 14-point deficit before the convention to a 2-point deficit just after it. But Reagan soon made it back, and won the election by a landslide 18.2 points.

With that history in mind, Dukakis pollster Irwin Harrison said he viewed the bounce more as an opportunity than an accomplishment. "The idea is to work as hard as you can to solidify what you got," he said.

Conversely, the bounce puts pressure on the Bush campaign. If Bush cannot match Dukakis' post-convention bounce, "it certainly does not augur well for an election success," said Lance Tarrance, a Republican pollster. "If they don't bring enough back to cancel out that bounce from the Democrats, then they're digging themselves into a deeper hole."