Summer heat may not only cause mirages in the desert, it may cause them in political polls, too.

Pollsters say people change their minds so much about political races during the summer that polls have trouble keeping up with them. And that may be one reason that two polls released Sunday disagree about who is leading in the close 1st District congressional race.A Deseret News/KSL poll conducted by Dan Jones & Associates showed Rep. Jim Hansen, R-Utah, leading by 10 points, 51-41, with 8 percent undecided; while a Salt Lake Tribune poll conducted by J. Roy Bardsley showed Democrat Gunn McKay leading by 5 points, 49-44, with 7 percent undecided.

The disagreement has both campaigns arguing about who is really winning and has some people criticizing the pollsters.

But, as the saying goes, both campaigns are apparently crying all the way to the bank. That's because the poll disagreement may actually be helping their fund raising. It shows potential donors that their campaigns are strong enough to win but that their opponents are also strong - so money is urgently needed.

"Actually, this is better for us, as far as fund raising goes, than if we were ahead by 10 or 11 points in both polls. If that happened, donations would slack off because people would think we had it won," said Peter Jenks, Hansen's campaign manager.

But why are the polls so different? The pollsters and politicians list several reasons.

First, the polls were conducted weeks apart, even though they were released the same day. So, actual standings may have changed between the time they were completed and reported.

The Jones poll was conducted July 27-28. The Bardsley poll was conducted Aug. 15-18. Because each poll normally asks questions regarding dozens of races and other issues, stories about results of individual questions are often spaced over a period of weeks. The Bardsley poll happened to be released right after the poll was completed, and the Jones poll had been finished for weeks.

That may cause trouble, pollsters say, because people change their minds so much about politics during the summer. "And I've never seen a year as volatile as this. Before the Republican convention, for example, the polls showed Dukakis ahead by 19 points. After the convention, they showed Bush ahead," Jones said.

Bardsley adds, "Summer is always a volatile period. Things will begin to settle down in two or three weeks, and then you won't see much change until the election."

Another reason the polls are different is that they each looked at slightly different groups. The Bardsley poll interviewed 188 registered voters living in the 1st District. The Jones poll interviewed 300 people in the district, whether they were registered voters or not.

Bardsley said that when he added in results from additional interviews with 36 non-registered voters, his poll actually showed the race is a dead heat.

A third point is that results of both polls are actually close when their possible error from the sampling process is considered.

Figures in the Jones poll are considered accurate within 5.5 percent, plus or minus, because of possible errors from sampling. So the actual views of district residents could be between the extremes of a 56.5-35.5 margin for Hansen (21 points) to a 46.5-45.5 edge for McKay (1 point).

The margin of error in the Bardsley poll was 7.1 percent. That means among registered voters, it predicts actual views could range from 56.1-36.9 for McKay (19.2 points) to 51.1-41.9 for Hansen (9.2) points.

In other words, results of both polls are essentially within each other's margin of error.

But that doesn't stop some in the campaigns from criticizing the pollsters.

David Dixon, press secretary for McKay's campaign, said, "I don't think Dan Jones is intentionally tampering with numbers, but it is interesting that he is also the private pollster for Jim Hansen and Norm Bangerter and his poll for the Deseret News shows Hansen ahead. I wonder what Hansen would be saying if Jones were our pollster."

Jenks says that comment is a cheap shot. "After a Bardsley poll in June showed us way ahead, Russell Clark (McKay's campaign manager) was quoted in the Ogden Standard-Examiner saying `Bardsley has a tradition of being inaccurate.' They attack whomever shows them behind."

The comment also upset Jones. "If I was in Hansen's camp so much, why did I call the election (two years ago) for McKay? I have to go with what my numbers say. I will never intentionally fudge any of my numbers."

Of note, both Jones and Bardsley said they have the highest regard for each others' work, but say such disagreements just happen. "It's not the first time polls have disagreed, and won't be the last," Bardsley said.