Homestretch scenario for Democrats

California could be the Mother Lode in the Democratic race for political gold. If Walter Mondale wins tomorrow's primary here, his hard-fought struggle with Gary Hart could be essentially at an end.

But if Senator Hart hits pay dirt in the Golden State, his strategists say he will carry the fight right onto the convention floor in San Francisco next month.

Several states vote in tomorrow's finale to the Democratic presidential race. But in the closing days, it has been clear that California, along with New Jersey, are the prizes that each candidate desperately wants.

The candidates have rushed from coast to coast, and from one end of California to another, at a dizzying pace. Adding to the problems of each has been a shortage of cash. Often, after a long day of speechmaking, the candidates have found it necessary to stage fund-raisers to get a little more grubstake for their campaigns.

Several scenarios are possible in tomorrow's voting. The results in each major state could be close. Here are four possible outcomes, and what each could mean:

Mr. Mondale wins both California and New Jersey. Several political experts say that would essentially end the contest.

Even a high-ranking strategist for Mr. Hart says it would be very difficult to carry on if Mondale wins in both states.

Mondale wins New Jersey, Hart wins California. This is what some experts expect. Winning in California would fire up the Hart campaign, and probably mean a continued scramble to win over uncommitted delegates prior to the July convention.

Mondale wins California, Hart wins New Jersey. While a victory in New Jersey would not help Hart as much as California, it would almost certainly be enough to keep his campaign alive.

Hart wins both California and New Jersey. The senator would then argue that Mondale, though ahead in delegates, had been rejected by millions of Democratic voters, while Hart had won most of the final primaries. At the very least, Hart would be expected to carry on a strong fight over party rules and the party platform. Mondale might be forced to strike some kind of compromise with the senator.

For Mondale, California is crucial not just in the race against Gary Hart, but in terms of the fall campaign against Ronald Reagan. It has become an important symbol.

Mondale supporters here are concerned that his candidacy, even at this late date, is failing to excite the voters.

One Mondale backer in San Francisco, for example, complains that the campaign has trouble drawing big crowds. When Hart held a rally in downtown Union Square, he easily drew 2,000 enthusiastic supporters. Mondale, just a few days earlier, attracted only 500.

''We've had real trouble getting our folks involved in Mondale's campaign,'' says one Democratic insider. On the final weekend prior to the primary, one Democratic organizer said he was able to get only 100 people in San Francisco to knock on doors for Mondale, compared with 300 in some other races.

A high-ranking Hart strategist, noting the lack of excitement among Democrats for Mondale, says of this race:

''Gary Hart has no intention of being a party wrecker. He doesn't want to do something to help the election of Ronald Reagan. But Hart has brought something new in the political dynamics of this race. What Hart has brought to this race has to be heard right through the convention.''

He then adds: ''It is hard to conceive of anything other than an all-out effort at the convention by Gary Hart.''

The Hart campaign's tally finds that in all the primaries to date, the senator is only 450,000 votes behind Mondale.

''We could wake up June 6 and find that we have a plurality,'' one Hart insider says. ''Further, if we run strongly on Tuesday, Mondale will not have won a primary west of Tennessee or Illinois.''

Hart, this insider says, could then go into the convention and ask:

''Are we simply going to hand the entire West to Ronald Reagan without a fight? That's what it would mean to give the nomination to Walter Mondale.''

Before he can carry that argument to the national convention, however, Hart must win California - a state with one of the most colorful and diverse electorates in the country.

The polls show Hart ahead here, but just barely. It's so close that few are willing to predict a winner.

Adding to the uncertainty here is the unusual nature of California's primary this year. Unlike most states, California has no ''beauty contest'' that pits Mondale, Hart, and the Rev. Jesse Jackson directly against one another.

Instead, the state is divided into 45 separate congressional-district contests. Voters will cast their ballots for delegates, not for the candidates themselves. In each district, the race is ''winner-take-all,'' so that with as little as 34 percent of the vote, Mr. Mondale, Mr. Hart, or Mr. Jackson could win every delegate in an individual district.

Further, not everyone's vote will be equal under the California system. In the Second District in Sacramento, for example, voters will be allowed to elect only four delegates to the national convention.

But in the 31st District in Los Angeles county, voters will elect seven delegates.

This system is designed to reward districts that are traditionally Democratic. But it will make it that much more difficult to determine who won and who lost the popular vote.

At present, Jackson is favored to win at least three districts. Hart and Mondale are expected to divide the rest.