San Francisco — For months the campaign for California's June 8 primary election followed a familiar script: some nominations, particularly Democrats Edmund G. Brown for US senator and Tom Bradley for governor, were virtually assured. Republican contests--especially the fight for the US Senate nomination--would be decided by the conservative Southern California vote. The massive peripheral canal project to speed additional water from north to south would be approved because the heavily favorable southern vote would overwhelm the dissent from the north.
But wait! Someone has been tampering with the script.
US Rep. Paul N. (Pete) McCloskey, the moderate Republican from Menlo Park in the north--seemingly mired in third place behind Rep. Barry Goldwater Jr. of Los Angeles and San Diego Mayor Pete Wilson in the contest for the GOP senatorial nomination--suddenly is almost head-to-head with his conservative rivals.
Southern Californians, warned by peripheral canal proponents that the project is the only thing that can save them from water shortages in future years, apparently are not so sure about that. Polls indicate that many more than expected will vote against it June 8, and unless the trend is reversed, the canal is expected to be rejected.
''Undecideds'' could still bring the outcome back in line with the original script. Meanwhile, the campaign has been delivered from uninterrupted dullness by these and one other development: Gore Vidal's intrusion into Governor Brown's cakewalk to the Democratic senatorial nomination.
It's not that famed author and television personality Vidal is given any chance of winning. He only claims a chance to ''make it interesting'' by picking up perhaps 30 percent of the vote to Brown's 50-plus in a four-candidate race. What seems to intrigue voters (and the press) is that Mr. Vidal is having fun in what he insists is a deadly serious campaign. Although the governor has steadfastly avoided direct confrontation, he, too, seems to enjoy trading arms-length ripostes with the author of ''Myra Breckinridge'' and ''Burr.''
On the Republican side, Congressman McCloskey is battling odds not as formidable as those faced by Vidal--but perhaps more frustrating. Having developed an apparently attractive northern California image as a moderate, McCloskey was labeled a ''maverick'' nationally when he briefly challenged Richard Nixon in 1972 for the GOP presidential nomination as a protest against the President's Vietnam policy. But to southern California Republicans, he is a liberal.
It is that label that many California pundits believed McCloskey could not overcome. But the feisty congressman, buoyed by the knowledge that he will get 35 to 40 percent of the Northern California vote in a multicandidate race, has spent most of his time in the south doggedly pursuing the 10 to 15 percent of the Republican vote that could give him a plurality--and the nomination--in an eight-candidate field.
Recent polls show Mr. Wilson in front, Mr. Goldwater second but continuing to slip, and McCloskey now a viable instead of a hopeless third. McCloskey and Wilson continue to stress the theme: ''I am the only Republican who can beat Jerry Brown in November.'' Wilson has clear advantages--momentum and lots of money for the crucial television blitz in the final days. But McCloskey's campaign is finally moving upward and his TV commercials, now beginning to be seen across the state, are thought by many observers to be more impressive than those of his rivals.
Goldwater's slump from long-term front-runner to vulnerable second is attributed to what has amounted to a phantom campaign. He has refused to debate the other candidates, avoided tackling the issues, and relied almost entirely on being the son of Arizona Sen. Barry Goldwater. In the face of vigorous opposition from McCloskey and Wilson, being a famous ''junior'' may not be enough this year.
Lt. Gov. Mike Curb rescued the Republican gubernatorial primary from its status as a Tweedledee-Tweedledum contest between loyal Reagan conservatives with his surprising stand against the peripheral canal. Many political pundits are not sure whether the unexpected opposition in the south to the canal has a direct correlation to Mr. Curb's rise in the opinion polls there. But it is beginning to look as though Curb will edge state Attorney General George Deukmejian for the right to run against Mayor Tom Bradley of Los Angeles, the certain Democratic nominee.
The canal referendum question is No. 9 of 12 on the California ballot June 8. The other propositions are:
1. To provide $495 million bonding for prison construction.
2. To remove the lieutenant governor as president of the state senate.
3. To protect tax rights of those whose property is expropriated by the state.
4. To provide judges wider scope for denying bail in felony cases.
5. and 6. To repeal most state gift and inheritance taxes.
7. To permanently index the state income tax.
8. To ratify a so-called ''victims' rights'' crime bill passed by the legislature.
10, 11, and 12. To ratify or reject congressional and legislative districts reapportioned because of the 1980 census.
Polls indicate that fewer than 40 percent of eligible voters are very aware of even the most controversial referendum questions - such as Propositions 8 and 9. Last-minute advertising campaigns, mostly on television, for and against the various propositions are likely to sway many, political observers say.