Polls are pointing to a potentially close general election race between George Bush and Michael Dukakis, with Jesse Jackson more hindrance than help as a Democratic vice presidential nominee.

Voter opinions change in the course of a campaign, and the recent round of surveys testing Bush against Dukakis, with and without Jackson, may bear no resemblance to the outcome six months from now, pollsters said in interviews this week.But the polls do establish a benchmark from which future movement can be judged, they said. And taken in context, the polls can highlight candidate strengths and weaknesses, providing clues to the campaign's likely course.

"We're not clairvoyant. This is the way it is right now. It's April. It's not November. It's close in April," said ABC News poll chief Jeff Alderman. "If Dukakis was trailing Bush by 20 points, we could say something now."

That lack of a big lead for the better-known Bush is one important result of the recent polls.

"It's not too early to know that it's a close race," said CBS News poll director Warren Mitofsky. "Obviously things are going to happen between now and November that will change this. That's what campaigns are all about. But it's fair to conclude that there's going to be a contest."

The biggest spread between the likely nominees was in a poll conducted April 21-22 for Time magazine: Dukakis had an 11-point lead over Bush, 50 to 39. A Gallup poll April 21-23 showed a virtual tie, Bush 45, Dukakis 43, as did a USA Today-CNN poll April 20-21, Dukakis 45, Bush 43.

History demonstrates that such early polls don't always predict the result. In late May 1984, an ABC News-Washington Post poll put Walter Mondale 11 points behind President Reagan among likely voters. Immediately after the Democratic convention, Mondale, on a crest of good publicity, pulled even with Reagan in some polls. But he lost in November by 18 points.

During the campaign, Mitofsky noted, Mondale came out for higher taxes. A similar "silly" move could cost Bush or Dukakis just as dearly, he said.

Because many voters have not made firm choices thus far this year, poll numbers are liable to "jump around," partly through differences in survey methods, said Andrew Kohut, Gallup's president. He said that could explain the Time poll's relatively large lead for Dukakis.

"One of the myths of the election was that the Democrats can't win," Alderman said. "The Democrats can win. I think people are beginning to see that now."

Recent polls did indicate an impact if Jackson ran as the vice presidential candidate. A ticket of Bush and Rep. Jack Kemp, R-N.Y., had a 10-point lead over a Dukakis-Jackson ticket, 50-40.