MANKATO, MINN., FEB. 9 -- Savoring his success in Iowa, Republican presidential contender Pat Robertson campaigned across the frigid snowscape of the northern prairie today as his strategists prepared to face the heat they expect from the press and their political competitors in the next few days.

"The people of Iowa gave me a big victory yesterday," Robertson told cheering audiences in Minnesota and South Dakota. He surprised many in his party by running a strong second to Sen. Robert J. Dole (R-Kan.) in Monday's Iowa caucuses.

But the candidate and his campaign manager, Marc Nuttle, mapped plans to deal with a series of problems they fear will surface now that Robertson has established himself nationally as a major player in the Republican race.

Campaign aides said they expect many TV news shows to play videotapes of Robertson's days as a fundamentalist preacher on television, when he regularly told audiences that he knew how to channel God's power to bring about financial, medical and meteorological miracles. Further, the campaign is concerned about an ongoing Internal Revenue Service audit of Robertson's ministry. And the candidate is scheduled to go to trial on March 8 -- "Super Tuesday" -- in a libel suit that could directly challenge his integrity.

The basic strategy to deal with such matters will be to come out fighting. "When people try to mock Pat's religious background, that's bigotry, and we're going to say so," Nuttle said.

Nuttle cited an interview Monday night when NBC's Tom Brokaw asked Robertson about talking to God -- and was immediately accused of "bigotry" by the candidate. "When somebody like Brokaw pushes it," Nuttle said, " . . . we're going to put it right back in his face."

Robertson seemed to be setting up defenses to such questions in his campaign stop here, where some people turned out via snowmobile in subfreezing temperatures to hear his brief speech.

"It's outrageous that people raised religious objections against John F. Kennedy as a presidential candidate because he was a Catholic," Robertson said. "And I think every American should have the right to the same kind of religious tolerance that he received in 1960."

In news interviews yesterday, Robertson worked to set up "expectations" that fit his campaign's prospects. He said that "the next major primary" is the one in South Carolina -- ignoring preceding elections in New Hampshire, Minnesota and South Dakota. Robertson has high hopes in South Carolina because Democrats are free to vote in the Republican primary there. Robertson evidently won support from many blue-collar Democrats in Iowa.

Asked about New Hampshire, Robertson said, "It's going to be difficult for me." He said he hoped to benefit from momentum he gained with his strong finish in Iowa.

He has considerably higher hopes for the caucuses here in Minnesota, to be held Feb. 23, one week after the New Hampshire primary. Robertson has drawn big and enthusiastic crowds here, and the Minnesota Republican Party has a strong "pro-life" element with ties to fundamentalist churches.

But even while Robertson is playing down expectations in this key state, he has a target constituency of some 50,000 donors to the Christian Broadcast Network's 700 Club here -- a potential core that could make him a serious competitor if he can tap it.

Political professionals who have been working New Hampshire say there are no signs of an "invisible army" there like the one Robertson tapped in Iowa, which network polls indicated was up to 90 percent born-again Christian. In New Hampshire, said Roger Stone, a top Kemp strategist, "I don't even see an invisible regiment."

But elsewhere, growing evidence has begun to emerge in such southern states as Louisiana, Arkansas, South Carolina and Georgia that Robertson has the potential not just to win isolated delegates but to win majorities in entire congressional districts, if not the state, in traditionally low-turnout Republican primaries.

"I'm telling everyone: 'Fasten your seatbelts,' " said Van D. Hipp, chairman of South Carolina's Republican Party. South Carolina will hold its primary on March 5, three days before the March 8 Super Tuesday contests in 20 states, most of them in the South. Because of this, the outcome in South Carolina is expected to influence the outcome on Super Tuesday significantly.

In Louisiana, the Robertson organization has been conducting an extensive program to switch Democrats to GOP registration. Steve Young, Robertson's state coordinator, said the program should produce more than 20,000 switches, and figures from the state election division support his claim.

During the last four months of 1987, before the switch program got into high gear, total state-wide registration had dropped by 15,000 votes, but Republican registration grew by 2,000, indicating that the drive has had considerable success.

"We've never seen anything like this, it's new to us," said Everett Zeagler, registrar of voters in Ouachita Parish in the northcentral part of the state. George Guidry, executive director of the Louisiana Republican Party, said Bush is still the favorite but "it could well be that a lot of people will be surprised."

In Georgia, the GOP held organizing caucuses in the precincts of the 10 largest counties. Robertson claims to have won control of the party in nine of the 10. Bush forces dispute the claim, but acknowledge that his backers now control at least three of the 10 major counties: Bibb (which includes Macon); Gwinnett, the fastest growing suburb in the nation, and Dougherty.

"Robertson has perhaps the single most powerful political machine in America to appeal to a small constituency," said an admiring Richard Wirthlin, pollster for the Dole campaign. Wirthlin said that in Iowa, the total Robertson vote resulted largely from capitalizing on the base of 40,000 donors to the 700 Club and CBN.

"The people in the South were wondering if I was electable," Robertson said at a news conference. "Indeed, Pat Robertson is electable . . . . The question that's been raised repeatedly during this campaign is whether I can broaden my base, whether the silent and invisible army was really out there," Robertson said. "Well, it turned out."

Robertson's surge, however, is clouded by his libel suit and a continuing IRS investigation into allegations that he illegally used tax-exempt funds from his television network and a foundation to finance the early stages of his campaign.

Robertson's top aides have made it clear that they would like to terminate the libel suit Robertson filed against former representative Paul N. (Pete) McCloskey (R-Calif.) after McCloskey charged that Robertson used political clout to avoid combat duty in the Korean war.

A federal judge has scheduled a trial in the case to begin March 8 -- meaning Robertson would find himself tied up in court defending his honesty for three weeks at the height of the primary campaign. Robertson hopes to settle the case out of court, but McCloskey has set tough terms for a settlement -- reportedly including a demand that Robertson pay all legal fees in the case.

To turn up the heat somewhat, McCloskey is scheduled to appear on morning news shows to discuss Robertson on the morning of March 8 -- just before voters in 20 states head to the polls.

On the IRS front, several former CBN employees and individuals involved in Robertson's political campaign have been interviewed in recent weeks by IRS agents, sources said yesterday. The individuals were asked about connections between Robertson's nonprofit Christian Broadcasting Network, the Freedom Council, which he formed to get Christians involved in politics, and his presidential campaign.

Despite Robertson's quiet organizing, a number of strategists remain very doubtful that he can translate his strength among evangelical Christians into substantial votes in states holding primaries with large turnouts. "For Pat Robertson to be a continuing factor in the nominating race, he's going to have to broaden that base," said David Keene, senior consultant to the Dole campaign. "I quite frankly don't believe he's going to be able to do that."