ST. PAUL, Minn. (AP) _ Mayor George Latimer is promising no ''fratricide and blood-letting'' in his challenge of fellow DFLer, Gov. Rudy Perpich, but the governor's partisans see a bitter intra-party battle brewing.

The Sept. 9 primary will pit the effervescent mayor who rejuvenated Minnesota's capital against a popular governor who counts big business among his admirers.

''It is a divisive problem, particularly one like this, which appears to be a personality contest,'' says Tom Berg, Perpich's campaign chairman. ''It takes you right back to the Keith-Rolvaag problem for the Democrats.''

The 1966 Democratic-Farmer-Labor primary fight between Lt. Gov. A.M. ''Sandy'' Keith and Gov. Karl Rolvaag sent a badly wounded Rolvaag to defeat at the hands of Republican Harold LeVander.

But Richard Broeker, Latimer's campaign manager, says there are vast differences between the Latimer-Perpich race and the Keith-Rolvaag campaigns of 20 years ago. ''The '66 situation is in a different universe,'' Broeker said.

Unlike Rolvaag, Perpich does not have strong ties to the DFL Party, having bucked the endorsement process in the past himself, Broeker notes.

Additionally, Latimer, 50, has vowed that he will refrain from personal attacks on Perpich. He is bypassing the June 13-15 endorsing convention and going directly to the voters.

Perpich, 57, followed a similar course when he returned to Minnesota in 1982 from Vienna, Austria, where he had worked for a Control Data subsidiary after his defeat in 1978. While he did not seek the party's endorsement, which was bestowed on former Attorney General Warren Spannaus, neither did Perpich challenge a popular incumbent, his supporters point out.

Perpich is the first governor in Minnesota history to serve non-consecutive terms. Lt. Gov. Perpich moved up in December 1976 when then-Gov. Wendell Anderson resigned to be appointed to the U.S. Senate seat given up by Walter F. Mondale when he became vice president.

Perpich lost the office in 1978 to Independent-Republican Al Quie, who did not seek another term, and regained it in 1982.

''By any measure, this administration in the last three years will be deemed a success,'' says Perpich. ''...I think the public is going to feel good about me and they're going to say, 'He's a good governor. We've come a long way. You better finish the job.' ''

As major accomplishments, Perpich cites a record $915 million tax cut in 1985 which dropped Minnesota's individual income tax from second highest in the nation to fifth or sixth, and figures that show 200,000 more Minnesotans are working than when he took office in 1983.

Until recently, Perpich was considered virtually unbeatable. But recent polls have given mixed pictures of his standing.

A statewide Northstar telephone poll April 4-13 showed Latimer favored by 38 percent of respondents who regard themselves as DFLers and Perpich favored by 36 percent. A Northstar poll in February showed Perpich favored 38 percent to 34 percent.

In an April 15-16 telephone poll conducted for Attorney General Hubert H. Humphrey III by Hickman-Maslin Research, Perpich topped Latimer 49 percent to 38 percent.

After serving 10 years as St. Paul mayor, Latimer says he is ready for a new challenge and the state is ready for new leadership of the kind he has exhibited in running Minnesota's second largest city.

''It's impolite and almost vulgar to reel off all the great things that have come to this city (during his tenure), but they are a fact,'' Latimer says.

Among the accomplishments he lists: $2.2 billion worth of reinvestment in a city that was dormant; a bond rating improved from AA to AA-plus; and awards, including the U.S. Conference of Mayor's ''City Livability'' award in 1985 and designation as an ''All-America City'' by the Citizens Forum of the National Municipal League in 1983.

While Latimer has proven vote-getting strength in Minnesota's capital, where he was elected to an unprecedented sixth term last fall, he has not been tested in a statewide race.

Supporters of Perpich, a native of northeastern Minnesota's Iron Range and a dentist by trade, are portraying Latimer as a big-city liberal.

The DFL governor has staked out a middle-of-the-road position on most issues and has cultivated close ties to the business community that Independent-Republican candidates complain have dried up their traditional campaign financing sources.

''If you go through the fund list of Gov. Perpich, it reads like a Who's Who of the Republican Party,'' said state Auditor Arne Carlson when he withdrew as an IR gubernatorial candidate after a seven-month campaign.

On the Independent-Republican side, former state lawmakers Cal Ludeman, Marion ''Mike'' Menning and Paul Overgaard were busily lining up delegates to the June 19-21 IR state convention when House Speaker David Jennings entered the race.

Jennings, a rising star who led Republicans in 1984 to control of the Minnesota House for the first time in 14 years, stunned the state's political establishment in March by announcing his retirement from public life. A month later, he changed his mind.