With a boost from Sen. Edward M. Kennedy, President Carter turned his campaign message into a stark contrast between "good guy" Democrats and "bad guy" Republicans today as he toured three critical Northeast states where he is running neck-and-neck with Ronald Reagan.

"There could not possibly be a sharper difference than that between me and Ronald Reagan or that between the Democratic Party of 1980 and the Republican Party of 1980," the president told a group of New Jersey labor leaders in Secaucus, N.J., this evening.

In an effort to bring back to the fold traditional Democratic voters who have strayed to independent John Anderson or remained uncommitted, Kennedy introduced the president to three Boston audiences and then flew to New Jersey to stand once again at the side of the president he challenged unsuccessfully in the primaries. Carter, meanwhile, campaigned also in Pennsylvania.

The president called the Nov. 4 election "a choice between progress and retrogression," and recited past Democratic battles for higher minimum wages, larger unemployment benefits, and Social Security against Republican opposition.

"My opponent says, 'Unemployment compensation is just a prepaid vacation for freeloaders.' This kind of philosophy permeates the difference between the Democrats and the Republicans -- it always has, it does now and predictably it will in the future," Carter told senior citizens at the Christopher Columbus community center in Boston's Italian-American North End.

Polls have shown that active campaigning by Kennedy could persuade many of the senator's supporters to support Carter on Election Day. In Kennedy's home state, Massachussetts, one of the few places where Anderson's strength is not waning rapidly, the senator's active support could be decisive. s

"Let's go to work," Kennedy told the senior citizens in asking them to help Carter. Still flirting with the presidency himself, however, Kennedy quipped to one member of the audience who invited him to tea: "I'll come back.Maybe in '82 or '83.

Throughout a long campaign day, Carter referred his audiences to the social programs of the New Deal and reminded them of the Depression of the 1930s. He described himself as a Democrat in the tradition of Franklin D. Roosevelt and John F. Kennedy. He warned the disaffected Democrats threaten to defeat their party's candidate this year and likened the situation to 1968.

"Had Democrats in 1968 given their support to a great man, Hubert Humphrey, Richard Nixon would never have been president of this country," Carter told a brief outdoor rally in Boston.

Carter resorted to a blatant payoff to quiet the largely high school-age crowd at the rally which greeted him with booing and a dozen hostile signs including several urging Kennedy not to "sell principles for peanuts."

Carter turned their boos to cheers by asking school officals to give the five schools of the area a day off Thursday. "Don't you forget, this is a Democratic holiday, not a Republican holiday, right?" Carter told them.

The president centered his criticism of Reagan on the GOP's candidate's past lack of support for the minimum wage, unemployment benefits and Social Security, but at a $500-a-head fund-raiser in Boston, he also assailed Reagan's promise to appoint a woman to the Supreme Court.

"What [Reagan] doesn't seem to realize is that equal rights for women involves more than just one job for one woman," Carter said. If Reagan believes in equal rights for women, he should support the Equal Rights Amendment, the president said.

In response to a question, he said intelligence sources have evidence that the American hostages in Iran are alive and well. He added that the United States has occasional communication with the three hostages being held in Iran's foreign ministry building.