Two major Michigan Democrats, worried about President Carter's consistent unpopularity in public opinion polls, are launching a campaign on Thursday to draft Sen. Edward M. Kennedy (D-Mass.) as the party's 1980 presidential nominee.

The draft-Kennedy organization is being led by Attorney General Frank Kelley and Bobby D. Crim, who serves as both the speaker and the majority leader of the Democratic-controlled House of Representatives.

While the state's senior U.S. senator, Donald W. Riegle Jr., said he has not decided whether to join the new Kennedy campaign, he made what clearly amounted to an endorsement of Kennedy and a repudiation of Carter in a speech last week to the state's chamber of commerce.

Sen. Carl Levin (D-Mich.) will not announce whether he will support Kennedy until after Kennedy declares his candidacy, according to Levin's press secretary, Jim Crutchfield.

The fledgling draft organization has already contacted Donald Tucker, a suburban Detroit attorney, who is spearheading Michigan's only Kennedy fund-raising drive. The new organization will play a prominent role in the effort, Tucker said.

Tucker has raised $2,000 "from a few casual phone calls" the past few weeks to help elect Kennedy delegates to the Florida Democratic convention in November. That convention will hold a straw vote of the delegates' presidential preference, and will be viewed as the first battle between Carter and Kennedy backers.

Tucker said Kennedy's most recent statements about a possible candidacy are "very encouraging" and tantamount to a go-ahead signal for his fund-raising campaign.

By endorsing Kennedy, the state party leaders put themselves at odds with Detroit Mayor Coleman Young. Young is spearheading Carter's Michigan reelection campaign and is planning an October fund-raiser for the president.

This split between Young and most other state party Democrats will be reflected in an upcoming vote in the legislature here to determine whether Michigan will retain its primary election or choose delegates to the national convention through a party caucus.

Political observers in the state have suggested that Kennedy could win a primary election "3 to 1, if the election were held today," according to one state senator. The move to kill the primary, which was ruled illegal by new Democratic Party rules, is headed for the most part by backers of Carter's reelection campaign.

"The party is officially neutral. The party has to stay out of primaries," one state Democrat who asked not to be identified said. "But every member of the House is on the ballot next year and they don't want a repeat of what happened with Johnson at the top of the ticket in 1966." That year, Democrats lost control of the state House.