The state Democratic Party's endorsement of Rep. James M. Shannon (D-Lawrence) for the Senate this month in Worcester appears more likely to confuse the race for retiring Sen, Paul E. Tsongas's (D-Mass.) seat than it is to clarify matters.

Although the 32-year-old Shannon beat Lt. Gov. John F. Kerry by 53.2 to 46.7 percent on the fourth ballot of the party convention June 9, Kerry, by most accounts, is still the narrow favorite to win the Democratic nomination in the mid-September primary.

Either Kerry, Shannon, former Speaker of the Massachusetts House David M. Bartley, or Secretary of State Michael J. Connolly will face the winner of the Republican primary battle between former Defense Secretary and Attorney General Elliot L. Richardson '41 and Walpole businessman Raymond Shamie.

Though no polls have been released in the two weeks since the convention, Kerry is expected to remain in front because he has high name recognition. He ran a successful statewide race for lieutenant governor in 1982--even after losing the party's endorsement--and he is positively identified with the popular administration of Gov. Michael S. Dukakis, an officially neutral observer in this race.

Kerry also stands to benefit from the active support of a number of local bigwigs, especially in the southeastern part of the state.

All of this begs the question: Why didn't he win?

Thomos R. Kiley, a Boston-based political consultant and chief of posting operations for the Kerry campaign, claims that Kerry did not expect to win the party endorsement, even though Kerry operatives invested heavily in Worcester and had what by all accounts was the best-run operation on the convention floor.

Kiley said that Shannon--who, for better or worse, has been labeled "Mr. Inside"--held all the cards at the convention, and had "the political leverage to work the inside game."

"We did put a lot of money into the convention, and that's the only reason we got as close as we did," Kiley added, "It was well worth the effort even in a narrow defeat."

Nonetheless, Kerry backers are terming the convention a "non-event" that was, and deserved to be, overshadowed by the Celtics 7th-game victory over the Los Angeles Lakers in the NBA Championships.

Kerry stands to benefit it this summer if the Senate race becomes a low-profile affair, hidden by the media glare of the Olympics, the Democratic and Republican National Conventions, and even Michael Jackson.

Come September, Kerry would win the four-man race on name recognition alone.

"Jim Shannon has the talent to do some damage but he has a roadblock in terms of media noise, the Olympics and the conventions," said political consultant Michael Goldman. "It'll be much harder to break through."

The convention victory has given three-term representative Shannon--until now little known outside his fifth district in Middlesex County--valuable statewide exposure, but it is now up to him to capitalize on the opportunity.

Shannon stands to benefit if Connolly--who barely made the 15 percent cut at the convention to stay in the race--fades away, as he is likely to do.

Shannon also showed strength among Bartley delegates at the convention. Though Shannon held, a 36-32 percent lead over Kerry on the first ballot, it took Bartley's withdrawal after the third ballot to put him over the top. Most of Bartley's support swung over to Shannon on the fourth ballot, finally giving him the nomination.

The Boston Phoenix last week reported that Bartley played kingmaker, intentionally pushing Shannon over the top, after he knew he could not win the endorsement himself. The article argued logically that Bartley--who commands substantial support from the moderate wing of the party and in his base in the western part of the state--wanted to neutralize Kerry's campaign with Shannon.

Yet, others say that Bartley did not try to manipulate his delegates, and would not have been successful even if he had tried. "We didn't tell out people what to do," said Bartley press secretary Cheryl A. Delgreco. "There wasn't that large of a vote swing to say David Bartley swung the vote."

Shannon, himself, told The Globe after his victory. "It was clear from the beginning the way this endorsement was going to be won was by being the second choice of other candidates' delegates. We knew for example that those Bartley people would come to us after he dropped out."

"We didn't make any deal with David Bartley," said Shannon spokesperson Marcia Hertz. "David Bartley does not necessarily have the power to sway his delegates. It's a little presumptuous to say that."

Shannon could also build his vote at the expense of Connolly, who is something of a maverick politician who commands a small but loyal following, mostly in Boston.

One informed delegate at the convention said that Kerry operatives made a conscious effort to lift connolly over the 15 percent cut-off on the second ballot Connolly had received a mere 8 percent on the first ballot and had to scramble for sympathy votes to keep him in the race.

"If Connolly were out of the race, that would have allowed Shannon to grow," the delegate said "keeping him in keeps that Irish vote split three ways and keeps the conservative vote split two ways."

Connolly and Bartley are considered more conservative than Shannon and Kerry.

Kerry clearly is vulnerable, although he appears still to be in good shape in 1982, many say he would not have beaten the popular Evelyn Murphy in the lieutenant governor primary race, had not four other candidates, two of them women, been running.

But Kerry has strong liberal credentials, and is best known as a Vietnam War hero who led the anti-war movement upon his return, Shannon, a protege of House speaker Thomas P. "Tip" O'Neill. Jr. (D-Cambridge), also has a strong liberal record in congress--he received a 96 percent liberal rating form the National Journal in 1982.

The result, said Goldman, will be a campaign that will concentrate on the minimal differences between the two, rather than on broader issues Kerry has labeled Shannon an establishment toady, though neither seems to have sprung a prominence from a wheatfield near Williamstown. Despite claims to the contrary, the Senate race is no reenactment of "Mr. Smith's Gone to Washington."