ST. PAUL, MINN., FEB. 21 -- On the stage of the World Theater, Jesse L. Jackson caught the spirit of Minnesota's latest hour in the political sun.

"This is the first time in 20 years that Minnesota has not had a favorite son running. Well, don't despair," the candidate told his audience at the Democratic presidential debate last Friday. "Let me be your favorite son."

Whereupon up popped Sen. Paul Simon (D-Ill.). "I'd like to be your other favorite son," he said.

The day before, speaking to students at St. Cloud State University, Simon tugged at similar strings. He told how his rural roots made him much like a Minnesota Democrat. And then, playing it to the max, he invoked the memory and farewell thoughts of the late Hubert H. Humphrey.

On the Republican side, the radio commercials for Sen. Robert J. Dole (Kan.) play to the man-of-the-heartland appeal. "Bob Dole. . . one of us," the ads intone. Rep. Jack Kemp (N.Y.), running hard here, portrays himself as the only true political heir to Ronald Reagan, the only true GOP conservative.

What it's about is Tuesday's political caucuses, when tens of thousands of Minnesota's Democrats and Republicans are expected to turn out to begin the complex process of choosing delegates to their national conventions. The Democrats will pick 86; the Republicans, 31.

For whatever that slender clout is worth, Minnesota has emerged as an important milestone along the political road to Super Tuesday, March 8, when 20 states and territories will hold primaries or caucuses that select roughly a third of each party's convention delegates.

The intensified campaigning here in recent days reflects Minnesota's importance. Simon and Kemp, in nearly must-win situations, arrived the day after the New Hampshire primary and went right to the stump. Jackson has kept a heavy schedule. Dole is scheduled for a last-minute visit; Massachusetts Gov. Michael S. Dukakis has returned for the ninth time in his quest for delegates.

If money and organizing prowess were the determining factors, the Democrats likely would choose Dukakis and Dole would be the GOP choice. Both are well-heeled, well-staffed and well-publicized. But in the view of strategists on both sides, Minnesota isn't that simple.

Although Vice President Bush has written off the state to the dismay of some of his partisans, Dole is expecting powerful challenges from Kemp and former television evangelist Pat Robertson, whose forces have been quietly organizing for months in rural areas.

Bush campaign aide Scott McPherson conceded that Bush's chances here are "slim to none" because "Minnesota is not that important in our national scheme of things." McPherson said he believed that "Pat Robertson is on top -- that's how I sense it," although Dole spent more than $230,000 here last year.

Floyd Brown, Dole's regional coordinator, expressed the same uneasiness about the Robertson forces. "Here, Robertson is clearly in the driver's seat. He has 70,000 donors {to the Christian Broadcasting Network's "700 Club"} here and if half of them turn out, he wins. . . .

The day after he stunned the party by finishing ahead of Bush in Iowa, Robertson made three stops in Minnesota. And his organizing, which began last October, has gone on apace with mailings, radio ads and home video shows aimed at getting his evangelical followers to attend the come-one, come-all caucuses.

"We feel it's going fairly well," said aide Teresa George. "We hear it is close between Dole, Kemp and Robertson."

Kemp, meanwhile, turned up the heat last week on Dole and put the Senate minority leader on the defensive. After Kemp called a press conference to accuse Dole of promoting tax increases and a freeze on Social Security benefits, Dole aide Donald Devine took the podium to defend his man.

On the Democratic side, the name of the game is "stop Dukakis," who has the benefit of presumed momentum from his New Hampshire primary victory as well as a strategy that focused early on Minnesota as a place to show his appeal beyond New England. He spent $159,000 here last year -- far more than his opponents combined -- and has more than 50 paid staffers.

There isn't much argument among the Democrats in a campaign remarkably devoid of name-calling -- unless the name being called is Ronald Reagan's. Even in their Friday debate, aside from former Colorado senator Gary Hart's futile efforts to provoke discussion of comparative records, there was only an occasional glint of real debate among them.

Even at that, most of the mild contumely was directed at Rep. Richard A. Gephardt (D-Mo.) for his sponsorship of trade legislation that the other candidates called protectionist and provocative to U.S. trading partners and injurious to U.S. trading interests.

Gephardt, short of money here after his all-out winning effort in Iowa, has made little effort to organize in Minnesota. "We just didn't have the resources to target," a key aide said. "Dukakis had the money and Simon has been better organized than we are."

Dukakis is the front-runner. Simon and Jackson, who campaigned vigorously this week appealing for funds to keep their efforts afloat, are thought to be running a close second, ahead of Gephardt. Hart and Sen. Albert Gore Jr. (Tenn.) are not considered to be factors.

The Dukakis campaign also has attracted the support of St. Paul Mayor George Latimer, former governor Wendell Anderson, millionaire Mark Dayton and Jim Nichols, the popular state agriculture commissioner. Nichols' presence on the team is noteworthy. He had been a vigorous backer of Gephardt's mandatory farm production control plan but switched to Dukakis after deciding the Missouri congressman had done little to move the bill in Congress.

"Minnesota has taken the governor seriously," said Dukakis' manager, Pat Forciea. "He has not come up here and made tremendous promises. . . . After New Hampshire, we have a heavy dose of enthusiasm. The night after New Hampshire we never had a better night on the phones. We worked on the undecideds and people who were leaning toward Simon. A lot of them broke our way."