Minnesota politicians, stunned by Sen. Hubert H. Humphrey's new cancer problem today, talked about the political implications were Humphrey to resign or die, but only off the record lest they sound crass and ghoulish.

In Washington, Humphrey's office spokesman said resignation had never been discussed. Here, the doctor who operated on the senator spoke of Humphrey's return to the Senate in early September.

Still, the speculation here that began when Humphrey underwent his first operation last year accelerated in both the Independent Republican Party (as it's called here) and the unique Democratic Farmer Labor Party (DFL) Humphrey helped father in 1944.

The top question is whether Minnesota might soon get another appointed senator. That decision would rest with Gov. Rudolph G. Perpich, a Democrat who appointed Sen. Wendell Anderson, to fill the vacancy left by Vice President Mondale. Perpich had been lieutenant governor, and succeeded Anderson in the governor's chair after Anderson resigned in return for Perpich naming him to the Senate.

A top DFL official predict that if Perpich were to appoint a successor to Humphrey, the party would be badly hurt. Anderson's popularity has dropped sharply since he became an appointed senator and Perpich is known to be considering alternatives to direct appointment.

One possibility would be his support of legislation, which lost in the state Senate earlier this year, to provide for filling a vacancy with a special election. Another possibility would be appointment of a replacement endorsed by a special DFL convention and a third would be the naming of a caretaker senator who would agree to resign after a special election could be arranged.

Talk of Perpich naming himself to the post or running for it is heavily discounted because of his apparent, zest for his current job.

Among the possible aspirants for a Senate seat is Rep. Donald M. Fraser, a liberal Democrat from Minneapolis, who has considered challenging Anderson when the senator bids for a full term next year. The DFL state Senate majority leader, Nicholas D. Coleman of St. Paul, has also been mentioned as a possible appointee.