Washington — Current political wisdom predicts that the Democratic race will end next month in a split decision that goes something like this: Walter Mondale will eke out a victory in New Jersey; but Gary Hart will win a bigger triumph in California, the nation's most populous state, which will bolster his claim that he is the better man to defeat Ronald Reagan in the fall.
But will Senator Hart really carry California, the gemstone of his native West? The latest poll out of the Golden State makes that very uncertain.
The California Poll, conducted by pollster Mervin D. Field, finds Mr. Mondale picking up strength despite Hart's latest string of victories in Ohio, Indiana, Nebraska, and Oregon.
The poll, completed Tuesday, shows the race too close to call. Mondale gets 41 percent, Hart 39, the Rev. Jesse Jackson 13, with 7 percent undecided. That's a significant turnaround from a month ago, when Hart led Mondale by 5 points.
Just as interesting as the newest numbers, Mr. Field says, is the unusual fragmentation of California's voters as they near election day June 5.
''I have never seen a primary like this,'' Field says. ''Voters are incredibly segmented by gender, age, and area of the state. There are unprecedented variations among the various segments, including income class, like I've never seen.''
Field offers these specifics:
Mondale leads Hart 45 to 36 in southern California, but trails Hart 35 to 42 in northern California.
Hart leads Mondale 44 to 41 among the state's white voters, but is far behind among black voters (11 to 32) and Hispanics (36 to 48).
Mondale carries the women's vote in California at the moment by a 44 to 34 margin; but Hart is ahead 44 to 37 among men. Even so, Mondale leads among men over 40 years of age by a 43-to-39 margin.
At the moment, Jesse Jackson isn't getting his ''normal'' share of the black vote, which has reached 70 to 80 percent in other states. His current 54 percent showing among blacks in California could very well improve in the closing weeks - a development that would hurt Mondale much more than Hart.
Hart's strength in the state has yo-yoed up and down by wide amounts since early this year. In February, prior to his come-from-behind upset in New Hampshire, Hart had only 5 percent support among California Democrats. That shot up to 42 percent last month, before settling down to 37 percent this week.
California has an unusual primary this year - one in which there could be some debate afterwards about who won and who lost. There is no statewide race for delegates, or even a statewide beauty contest. Instead, there are separate contests in each of the state's 45 congressional districts. Ballots will list the names of delegates, and voters will cast their ballots for delegates rather than directly for the presidential candidates.
For example, in the 28th District, which includes Culver City and parts of Los Angeles and Inglewood, voters will elect eight delegates. If the eight Mondale delegates in the 28th District get the most votes, Mondale will get all eight delegates to the national convention.
This system means that when the election is over, there will be no clear-cut tally that indicates which candidate ''won.'' In fact, it will be possible, because of the California system, for a candidate to get proportionally more delegates than he does votes, if the votes are well distributed.