Democratic activists dig in.

With less than 50 days until the 1984 presidential election, Democratic activists in New York, New Jersey, and Connecticut have no illusions about the task before them.

The Walter F. Mondale/Geraldine A. Ferraro ticket is neck and neck with Ronald Reagan/George Bush in New York. And the President, who enjoys a lead in both New Jersey and Connecticut, has been broadsiding the Mondale campaign in the Northeast.

Mr. Reagan has made several campaign stops in the area within the last week - Sept. 12 in upstate New York, and Wednesday in Connecticut and New Jersey.

After the hoopla of the Democratic National Convention in San Francisco this summer, many Democrats had returned home ready for a good fight. Now there are some doubts - about the ticket, about attention to personality rather than issues, about what will happen within the party if Ronald Reagan is reelected.

''We haven't done any polls here, but the ones I've read have not shown it to be a good year for Democrats,'' says Alberta Jagoe, mayor of Milburn, Conn., and a Hart delegate at the convention. ''We're hoping voters will support our local candidates.''

Lawrence Mandelker, a New York lawyer who lives in Westchester County, was also a Hart delegate, and left the convention in an ''upbeat'' mood. But he doesn't think Mr. Mondale should feel too cheerful these days. He predicts a Reagan landslide.

The Democratic team needs to put forth a unifying theme, which it has not, says Mr. Mandelker. Mondale needs to project leadership capabilities and skills that will make the voters feel comfortable leaving the country in his hands.

''He doesn't, and Reagan does,'' says Mandelker. ''Regardless of the issues, people feel more comfortable with Reagan.''

There is some optimism. Robert Zimmerman, a marketing executive on Long Island, is an enthusiastic Mondale delegate who is now busy stumping for the candidate locally.

''The summer was difficult,'' admits Mr. Zimmerman. ''But I think the campaign is on track now.'' He says both Mondale and Ms. Ferraro are now articulating that they offer a strong and different choice.

''I don't think (Reagan's) popular appeal replaces the very real questions and concerns of people,'' Zimmerman says. ''All the hype surrounding Reagan doesn't erase the problems families face.''

In Buffalo, where Reagan visited last week, City Councilor James Keane, a Mondale supporter at the convention, has no doubt that his city will endorse the Democratic ticket. But Erie County, which includes Buffalo, is a toss-up right now, even though it has consistently gone Democratic in the past.

But Mr. Keane predicts the county will deliver a solid Democratic vote ''once we get word out what our 'wonderful' president has done to the economy locally.''

He points out the Erie County is on the brink of bankruptcy, much of it due to a greatly increased welfare roll. The question, ''Are you better off now than you were four years ago?'' will not play well in Buffalo.

''This is not San Diego,'' says Keane, who insists that Reagan's policies are pro-Sunbelt at the expense of urban centers in the Northeast.

Indeed, many Democrats are hoping that issues such as this will take center stage in the election, particularly now that debates between Mondale and Reagan, and between the vice-presidential candidates, have been arranged.

The issues these Democrats would like to see raised? Reagan's military spending record and lack of arms negotiations. Civil rights and ''fairness'' to minorities, women, and the poor. Education. The environment. The federal deficit.

Right now most delegates returned from the convention are working for the Mondale-Ferraro campaign, even if they were supporting other candidates.

In Milford, a shoreline town whose main employers are the makers of Bic pens and Schick razors, Mayor Jagoe will make sure telephone calls are made and pamphleting is done. Councilman Keane says Buffalo will receive literature, television and radio ads, public debates, in addition to the traditional ''hand-pumping'' and door-to-door efforts.

Joyce Morgan, a Jesse Jackson delegate from Newark, New Jersey, says the Rainbow Coalition is working to keep up the record minority voter turnout that was seen in June's presidential primary.

''We want to encourage people to come out to make them feel this election is important,'' says Ms. Morgan, who works for Mayor Kenneth Gibson's clean city campaign.

''The Democrats failed, not us,'' says Katie Hall, a Jackson delegate from Brooklyn and an administrator in a New York hospital, Ms. Hall. ''We - blacks, whites, Hispanics, Asians - did a yeoman job, helping to put a black man on the podium at the convention.''

But, she says, the Democratic Party did not respond to the efforts of this coalition and stuck with politics as usual. Voter participation among Jackson supporters, she adds, may not be as strong as it was in the primary.

Both Hall and Morgan say that Democrats will have to take a harder look in the future at the voters Jackson represented. Others agree that the Democrats need to open up more to others.

Mayor Jagoe supported Gary Hart because of his Senate record, and because she felt he would attract more people into the party.

Lawrence Mandelker says the Democratic Party is still on target, but that Walter Mondale is being skewered on the personality issue. He points to polls that show many people agree with Mondale on various issues, but they like Ronald Reagan as a candidate.

But, says Mandelker, the GOP is painting itself into a corner and will face a disaster in 1988 unless it recaptures the center of its party.

Although the Republicans have accused the Democrats of moving too far to the left, Mandelker says the Democratic convention showed that his party had moved back to the center. It is the Republicans that have ''lurched far to the right.''

''The landslide I predict will be a personal victory for Reagan, and not a party victory,'' says Mandelker.