Primaries forcing front-runners to sharpen campaigns; Super Tuesday results leave Democrats with no clear-cut front-runner and a long way to go

This is a presidential race people won't soon forget. Super Tuesday's vote in nine states was once expected to settle the Democratic campaign for the White House. Instead, it has sent candidates, pollsters, and reporters hurrying toward the next big contests in search of the eventual winner.

The experts are scratching their heads. For once, they admit they really don't know what is going to happen next.

There was good news in the Super Tuesday vote for both Gary Hart and Walter Mondale. But there were also trends in the voting that concern each camp.

Momentum is now the key for both Mr. Mondale and Senator Hart. Mondale once had it. Hart enjoyed it after New Hampshire.

But after Super Tuesday, the momentum in this race appears to have shifted, with no candidate clearly in control.

Even before Tuesday, political analysts had picked up the first indications that something was changing. The evidence was sketchy. But it suggested that Hart's stunning momentum during the past two weeks had begun to slow.

Tuesday's vote indicated that Hart's support may be reaching a plateau, which could make it much harder for him to wrap up this campaign without a long, hard fight.

The Mondale-Hart race, according to some analysts, could now turn into a political marathon, extending right through spring and into the national convention in July.

Super Tuesday, however, did settle a few things:

* Gary Hart could claim the title of front-runner. His impresssive victories in New England, Florida, and the West have proved that he is the man to beat, and that he can win races outside the Northeast.

* Walter Mondale gained his second wind - and for the first time defeated Senator Hart in a primary vote, with triumphs in Georgia and Alabama.

* Jesse Jackson, after faltering in New Hampshire, showed great strength with Southern black voters, and said he will stay in the race to the end.

* George McGovern, finishing third in Massachusetts, dropped out of the race.

* John Glenn, although running strongly in Alabama, placed a weak fourth in two other states where he should have done well, Georgia and Florida. His future is uncertain.

For Hart and Mondale, Tuesday was the kind of good-news, bad-news day that made each realize that this struggle wasn't going to be easy.

First, a look at the race from Hart's perspective.

Hart campaign manager Oliver Henkel Jr. had set one major objective for Tuesday. That was to prove that Senator Hart is a true national candidate, a Democrat who can win in every section of the country.

He did just that. Mr. Henkel once thought that Alabama would be Hart's best Southern state. But it was Florida that came through for the young Colorado senator.

Even harder tests may lie just ahead for Hart, however.

The next critical contests are in the Midwest and South, and almost none of them will fall effortlessly into Hart's lap. In the Midwest, Mondale is favored in the important Michigan caucuses on Saturday. He is also expected to do well that same day in Mississippi and Arkansas.

Those caucuses will be followed quickly on Tuesday by the pivotal Illinois primary, where labor is a big factor. That shapes up as a nip-and-tuck race between Mondale and Hart.

Behind the scenes, there are other concerns for Hart.

During the past few days, political analysts picked up the first indications that Hart's momentum was slowing. This was expected. The impact of his surprise victory in New Hampshire couldn't last forever. He also enjoyed a spurt of publicity in the news media; and there was a natural curiosity about him as a new national figure.

But his new prominence also drew attacks from his four opponents. They apparently hurt.

There was further evidence that Hart may be peaking, according to exit polls conducted during Tuesday's voting.

An example of this could be seen in Alabama. A week ago in that state, according to ABC-TV surveys, Hart was picking up three new supporters for every one that shifted to Mondale. But by Monday of this week, Mondale was picking up new supporters twice as fast as Hart.

The turnaround, especially in the South, appeared to come about after Mondale began ripping into Hart's voting record in Congress and to question Hart's claim that he is the candidate of ''new ideas.''

Mondale told crowds in the South that when he heard Hart make his new-ideas claim, he was reminded of the current TV ad for a hamburger chain that challenges its rivals with the question: ''Where's the beef?'' He implied Hart's that new-ideas theme was nothing more than a fluffy hamburger bun with no meat inside.

At the Mondale campaign's celebration party Tuesday night, the jubilant crowds greeted Mondale with cries of ''Where's the beef? Where's the beef?'' - obviously enjoying the joke at Hart's expense.

If the survey data are correct, Hart may have to make a greater effort to put more protein into what he dishes out to the public.

Mondale, however, also has concerns.

His campaign relies heavily on support from organized labor. That's the key to victory in Michigan on Saturday.

But on Super Tuesday, it was shown once again that union leaders are not always able to deliver the union vote to Mondale. In Massachusetts, union members split 42 to 26 in favor of Hart, according to ABC exit interviews. Only in the South did union lines hold - especially in Georgia and Alabama, where union voters went more than 2-to-1 for Mondale. It is notable that those were the only two primaries that Mondale carried.

Will Mondale's union support help him in Michigan and Illinois? That remains an important, but unknown, factor.

There's are two other concerns for Mondale.

He's using up his money fast. There are estimates that at the pace he is going, Mondale could run low on funds by the end of April, with more than a month of primaries and caucuses left.

Mondale ''front loaded'' his campaign efforts in hopes of knocking out all the competition fast. Hart aides say they plan to ''back load'' their campaign, pouring the greatest amount of funds into the final races. That could spell trouble ahead for Mondale.

Another concern: Where will the John Glenn support go if he gets out of the race? CBS-TV exit data indicate that most Glenn supporters would have pulled the voting lever for Hart if Senator Glenn hadn't been in Tuesday's primaries.

The same network study found that most of George McGovern's strength in Massachusetts would have gone into the Hart column if Mr. McGovern hadn't been in the primary.

For Super Tuesday's also-rans - McGovern, Mr. Glenn, and Mr. Jackson - the outlook is mixed.

McGovern, in dropping out, said he felt satisfied that his entry into the race had raised issues that would not otherwise have been discussed. Unlike most of the others, he wanted to see the Reagan defense budget severely cut.

Jackson could feel a certain vindication in the results. He had been opposed by many black leaders in the South, including Coretta Scott King and Georgia state Sen. Julian Bond. Many blacks felt a vote for Jackson would have little impact on the eventual choice of the party's nominee. Jackson's strong showing in Georgia (21 percent) was only nine points behind the winner. He called that a missed opportunity for a tremendous upset if all blacks had backed him.

Glenn had hoped for a breakthrough in either Georgia or Alabama. He could claim that his actual vote in Florida, Georgia, and Alabama was twice as high as the polls said it would be. In fact, exit data found Glenn was picking up speed in the final few days before Super Tuesday.