AMES, IOWA, SEPT. 12 -- Hundreds of placard-waving supporters of television evangelist Marion G. (Pat) Robertson overwhelmed the first major Republican presidential campaign event of the fall tonight, giving Robertson a stunning upset in a straw poll at a major party fund-raiser.

Robertson supporters, outfitted in distinctive red, white and blue T-shirts, easily outnumbered and outshouted backers of four other GOP aspirants at Iowa State University for a "Presidential Calvacade of Stars."

Robertson, dismissed as a fringe candidate with little widespread appeal before the event, won 34 percent of the straw vote. Senate Minority Leader Robert J. Dole (R-Kan.) was second with 25 percent. Vice President Bush, who was favored to win, was third with 23 percent.

He was followed by Rep. Jack Kemp (R-N.Y.) with 13.5 percent, former Delaware governor Pierre S. (Pete) du Pont IV with 4 percent, and several lesser candidates.

"I'm absolutely overjoyed," declared a smiling Robertson. "It's an indication in my view to what is going to happen in the Iowa caucuses" on Feb. 8.

Robertson and spokesmen for other campaigns were quick to claim that the results had damaged Bush's status as front-runner in the GOP race.

"I dare say he's going to be slipping in the polls," Robertson said. "It's been said his support is very broad, but not very deep."

"This is a bad night for George Bush," said Kemp campaign manager Charles Black. "He is the front-runner and when you're the front-runner you have to win."

The event, attended by 5,700 Republicans who paid $25 each for tickets, was seen as the first major test of the political organizations that the candidates have spent months building here.

The strong Robertson showing caught most of his rivals by surprise. Leaders of Bush's campaign were fast to get the message.

"This event is very much an organizational contest. And they {Robertson's campaign} have demonstrated they have organizational clout," Rep. Thomas J. Tauke (R-Iowa), cochairman of Bush's Iowa campaign, said before the results were tallied.

Tonight was the first night Bush has appeared on the same platform as his rivals for the GOP nomination, and he took some criticism from them.

Du Pont said that Bush for a long time "seemed to want to run from the entire campaign, to take his name-identification lead and his perks as vice president and stake his claim on the nomination without ever telling us what a Bush administration would do if he were president."

"But George, it is a tough way to win and a tough way to govern," he said. "Ronald Reagan didn't get elected by being a 'from-runner.' "

Bush made it clear earlier in the day that he had no intention of attacking his rivals. "I want this nomination to be worth something after I win it, so we can go out and whip those seven dwarfs in the fall of next year," he said, referring to the Democratic contenders.

Bush used his allotted 15-minute formal speech to refurbish his foreign policy credentials by repeatedly referring to meetings with allied leaders and to distance himself from corruption in the Reagan administration.

"I want people in government who want to make a contribution, not to make a buck," he said. "You can be sure of this -- a Bush administration will be known for its integrity."

Bush won a straw poll at a similar GOP fund-raising event eight years ago when he was relatively unknown in Iowa, giving his fledging 1980 presidential campaign a major boost.

This week his rivals argued that the pressure was again on the vice president to win the straw balloting.

Bush's campaign rented buses to bring supporters here, mailed 10,000 letters to supporters and made thousands of telephone calls.

But Robertson's efforts at building a crowd were far more successful. In the end almost twice as many people showed up for the event as expected. Many were Robertson supporters. "Jesus is Coming," said a signed carried by one.

Marlene Elwell, Robertson's Midwest coordinator, said the turnout demonstrated that the evangelist "is a viable candidate, that he is electable."

Bush didn't acknowledge the Robertson crowd. Dole did, declaring, "I'm very thankful to Pat Robertson and others who bring a lot of new people to the Republican Party."

The straw poll was preceded by a frenzied round of speeches, rallies, parades, receptions and news conferences.

To vote in the poll, a person needed to present a $25 ticket to the fund-raiser and an Iowa driver's license.

Sen. Charles E. Grassley, the state's most popular Republican officeholder, picked the day to announce his endorsement of Dole. "He is not only one of us, he can win," Grassley said.

Dole also said he is winning a straw poll being conducted by an ice cream company here. "It's easier to buy that one," he said. In the ice cream poll, each candidate is assigned a flavor and votes are based on the amount of each flavor sold.