Speculation persists that Sen. Muriel Humphrey, (D-Minn) does not intend to run for the remaining four years of the term of her late husband, Hubert.

The appointed senator, who is 66, was the star attraction last night at the first annual Hubert H. Humphrey Dinner - formerly the Jefferson-Jackson Day Dinner - in the St. Paul Civic Center, a fund-raising event for the Democratic Farmer Labor Party that drew 5,000, many of whom paid the maximum $100 ticket price.

On her decision hinged a series of developments, chiefly the chances of Rep. Don Fraser's election to the Humphrey seat. Fraser has gained strength in the county conventions that select delegates to the state convention in June, while Humphrey received standing ovations but little tangible support.

Fraser's campaign staff said he is already at the 50 percent mark for endorsement at the June convention of the Democratic Farmer Labor Party, as the Democrats are officially known in Minnesota. It takes 60 percent to be endorsed.

The gathering here was staged as the largest Minnesota tribute so far for Hubert H. Humphrey, who died last Jan. 13 of cancer. His widow was appointed on Jan. 25 by Democratic Gov. Rudy Perpich to serve until next January, as the law provides. But she put off announcing whether she'd try to retain her Senate seat. She has enjoyed holding it, but the election campaign would tax her health and endurance.

According to friends, she was "absolutely exhausted" after attending two county delegate conventions last Saturday. Concern for her health dates to the physical and emotional strain of her husband's last illness. In December she was hospitalized for what her office subsequently described as "exhaustion that had bought on an irregular heartbeat, which cleared pu even before the hospitalization."

She also had gall bladder surgery last April. She denies having a heart ailment, but has said she has high blood pressure.

She told the conventions last Saturday in Wright County (where her Waverly home is situated) and in McLeod County that she had a difficult time deciding what she should do politically. At the Wright County convention only two of the 14 delegates were elected as Humphrey delegates to the state convention. At the McLeod convention a majority of the delegates favored Fraser in a straw ballot, and one Humphrey delegate and five Fraser delegates were actually elected.

Helga Nielsen, 71, McLeod County chairman and Fraser supporter, said "We all love her, but many of us don't think she should run." For herself, the senator said:

"My kids say to me, 'Grandma, the grandchildren need you at home. Don't forget you are 66 years old.' I don't fell like retiring, so you can see how torn I am."