Freshman Sen. Richard B. Stone is the favorite to win Tuesday's Democratic primary in Florida, but not by a margin big enough to avoid a runoff election.

Five other Democrats and six Republicans are running for the Senate this year and all have made Stone their target, accusing him of flipfloping on issues, failing to help the state cope with the influx of Cuban refugees and raking in too much money from special interests. His campaign contributions total $1.4 million.

Stone's low-key campaign has lately hit on conservative themes. He enlisted the support of former representative Robert L. F. Sikes, whose reprimand by the House did nothing to diminish his reputation as a hawk on defense spending. Stone also helped circulate a letter of support written by former backers of George Wallace's presidential campaign.

Last weekend, the Jewish Harvard graduate returned to his 1974 campaign from when he whipped out a harmonica and played "You Are My Sunshine" at an outdoor chicken dinner in Tampa.

Bill Gunter, Florida treasurer and insurance commissioner, and former state senator Kenneth (Buddy) MacKay have a shot at getting into a runoff with Stone, with Gunter the most likely to do so.

A statewide poll by the St. Petersburg Times and three other newspapers Sept. 2-3 found Stone leading the field with 29 percent of the vote, followed by Gunter with 24 percent and MacKay with 18. An analysis of the voters most likely to go to the polls found MacKay and Gunter nearly even, however, but still behind Stone. Almost one of every five respondents was still undecided.

The Republican race Tuesday is likely to produce a runoff between former public service commissioner Paula Hawkins, now leading in the polls, and former representative Lou Frey.

Hawkins leads the Republican field mainly because she has made the biggest name for herself. The statewide office she held until last year gave her publicity all over Florida, often as a consumer advocate.

The same poll showed her drawing 32 percent of the Republican vote, Frey 20 percent and the four other candidates 10 percent or less. A big block -- 28 percent -- still hadn't made a choice in the unusually quiet race.

Both runoffs would be Oct. 7.