Des Moines — A survey of nearly half the Democratic county chairmen in Iowa indicates that Walter Mondale should win a decisive victory here in the nation's first presidential caucuses next Monday.
The survey, conducted by the Monitor during the past two weeks, also found that Gary Hart could prove to be a surprise in the field of eight candidates with an unexpectedly strong vote.
Senator Hart, whose presidential hopes were almost written off by the news media last fall, has made significant inroads in Iowa's rural counties where Jimmy Carter gained much of his strength in 1976.
It is widely predicted here that John Glenn will place second in the voting. The county chairmen generally agree with that assessment. But they indicate that Senator Glenn's second-place position is probably weakening in the final days here.
The man to watch, however, is clearly Mr. Mondale, who hails from next-door Minnesota, and who could sweep every region of the state, the survey found.
Every chairman who was willing to predict an outcome, from Kathryn Hansen in Sioux County near the South Dakota line, to Philip Wise in Lee County near the Illinois border, judged Mondale to be the front-runner.
Even if Mondale wins a sweeping victory in Iowa next week, many of the chairmen see a difficult campaign ahead here against President Reagan in the fall. The party chairman in a small northeast Iowa county said:
''If Mondale is the nominee, he will not be able to shake the big-spender image. Somehow Reagan has escaped the label.''
Senator Hart's apparent strength just a few days before the voting begins in Election '84 would have been predicted by almost no one a few months ago. His campaign was in debt. His staff was being cut back. Some news analysts had virtually written him off.
Faced with this grim outlook, Hart went to the grass roots. He has crisscrossed Iowa, speaking to small groups, cultivating farmers and townspeople in the thinly populated countryside.
Hart's strategy is one that has worked here before. In a 12-month period during the 1976 campaign, Jimmy Carter spent 109 days in Iowa, much of it in rural areas. Mr. Carter sank down some deep roots with Iowa voters, roots that have survived. Today, surveys show that Iowa Democratic voters more strongly support the record of the Carter-Mondale administration than any other group of Democrats in the nation except those in Georgia.
Hart appears to be nurturing that kind of deep-rooted support, the survey indicates. Here's what some of the county chairmen have to say:
Terry Stewart of Dubuque County observes that ''Hart . . . is gaining ground in these closing weeks, as a youthful, creative candidate.''
James Miller of Henry County says: ''Hart has worked hard in Iowa and a lot of people like him. He has gotten to the people.''
Del Laird of Buena Vista County observes: ''Mr. Hart is coming up fast on the rail.''
W. R. (Bill) Monroe of Des Moines County indicates that Hart supporters have strong commitment.
Ron Stopak in Plymouth County concedes that Hart lacks national recognition, but adds: ''In Iowa, Hart seems to have good crowds for an unknown, and people have left impressed. In Iowa, as opposed to a large media state, word of mouth is helping Gary Hart's campaign.''
Mary Kay Kenworthy of Decatur County says: ''Hart seems to be the only candidate with momentum. Although many people are still undecided, it appears Mondale will be the favorite. Both Hart and (Alan) Cranston are well organized and are generally liked by the undecided group.''
Red Brummer, Joan Hutson, and Lois Hatterman from Harrison County all suggest that Hart could be the surprise candidate of the campaign because he offers ''fresh ideas. We are tired of old cliches. . . .''
Rich Landis of Muscatine County suggests that Hart could benefit because he has ''recruited some highly dedicated and influential local people.''
The Monitor survey covered 47 of Iowa's 99 counties, and included all of the major regions.
Of the chairmen surveyed, 43 said Mondale would come in first in the caucuses next week. Glenn was usually placed second, with either Hart or Cranston in third place. Only four chairmen, including Rita Goodenow of Ida County, refused to make a prediction about the outcome. ''It's difficult, if not impossible, to determine which candidate is ahead in Iowa at this time,'' she said. What is really ahead, she suggests, is ''I don't know.''
Why? ''People tell me they don't particularly like any of the candidates, for one reason or another. They also tell me that they suppose Mondale will win because the media say he will. . . . Even those people whom I find are supporting Mondale tell me they do so because the media say he will win and they want to be with the winner.''
Rita Goodenow's observation that the ''I don't know'' answer could be ahead is not without support from others. Political canvassers making telephone calls to all corners of Iowa say that from 30 to 50 percent of the voters indicate that they still haven't made a choice among the eight major Democratic contenders here. While many of those probably won't bother to go to next Monday night's caucuses (the Mondale people hope they won't because many of them would probably vote for someone else), many will attend. And if past tradition holds, many will vote to send Iowa's delegates to the national convention uncommitted.
It is often forgotten that in 1976 Jimmy Carter ''won'' the Iowa caucuses with 29 percent of the vote. In fact, Carter came in second behind ''uncommitted ,'' which had 34 percent.
In 1980, in an emotion-filled race between President Carter and Sen. Edward M. Kennedy of Massachusetts - a race in which very few people here felt neutral - the uncommitted vote fell to only 10 percent. But with less emotionalism involved this time, and without such gripping issues as the grain embargo and the Iranian hostage crisis to stir the voters, the uncommitted total is again expected to rise.
Besides an increase in Hart support, there are other developments that may be worrisome to front-runners Mondale and Glenn.
Senator Cranston has put in place a very strong organization that is expected to do an excellent job turning out pro-Cranston people on caucus night.
Former Sen. George McGovern remains a sentimental favorite with many Democratic activists, and could get a substantially larger vote than predicted, in the view of some chairmen. Reubin Askew, emphasizing the abortion issue, is also an unknown factor. He has worked outside the usual party channels and could draw support from conservatives and Roman Catholic voters, several chairmen said.