The sound of Hawaiian music swells. The surf laps gently in the background. A voice says:

"June 14, 1978, Gov. Brown and the legislature, both Democrats and Republicans, were working hard to pass a new law to implement Proposition 13. Time was short. Dozens of tough legal questions had to be answered. On that same day, Attorney General Evelle Younger, Gov. Brown's Republican opponent, was enjoying the cool ocean breezes of Hawaii."

That radio spot, which has been playing for some two weeks here in California, says almost everything there is to say about the most important political race in the country this year. It announces the issue, the early start, the intense and highly personal pace, and the probably outcome.

The issue was decided in the June 6 primary, which also determined that Gov. Jerry Brown would be opposed in his race for reelection by Younger. That day the electorate approved by a hugh majority the big cut in property taxes, and the limitation on future taxes, mandated by Proposition 13. Ever since, the dominant political question in the state has been how to maintain services now and in the future while putting into effect the immediate tax cust.

Brown, who had opposed Proposition 13 in the primary campaign, switched sides and became its chief exponent. He developed a program for distribution of a massive state surplus in ways that cause only marginal reduction in services at present. For the future, he has named a bipartisan blue-ribbon commission to determine new constitutional provisions for state fiscal policy.

Younger, a veteran officeholder who specializes in maintaing a broad range of support, did not immediately take a position on Proposition 13. Nor did he push himself forward. Instead he moved to make the election an up-of-down referendum on Brown.

"The issue," he told me in an interview right after the primary, "is Brown's integrity." A couple of weeks ago his campaign began the battle of the radio spots. It put out a series comparing remarks made by the governor against Proposition 13 before the primary and for Proposition 13 afterward. The spots underline the contrast between "the old Brown" and "the new Brown."

Brown is hitting back in an intense and not impersonal way. His campaign has developed the theme that Younger is a big spender, used to living off the public payroll and therefore not fit to manage California affairs in a time of fiscal stringency. The Brown campaign has shown that Younger took vacations at public expense in Hawaii and Mexico, used public monies to add showers in his offices in Los Angeles and San Diego, and to purchase Lincoln Continentals as office cars. There has also been a charge of conflict of interest, alleging that, as attorney general, Younger failed to prosecute a case against Exxon and asserting the reason was that Mrs Younger had some shares of Exxon stock.

Brown acknowledges that the early footing is fast and furious, and offers two reasons. First he says that "Younger is invisible. He campaigns in the smaller towns and avoids the networks. He gives you his record - FBI man, judge, district attorney. But he doesn't say what he did. So we have to show the people of this state what he did."

Brown further acknowledges that his own support for Proposition 13, and his first term as governor, alienated many traditional Democratic groups. "I've got a lot of bases to touch," he said in an interview, and cited lawyers, doctors and lumbermen. A typical schedule a couple of days ago included two television interviews, a session with black ministers, another session with black college students and three visits with white middle-class groups in the San Francisco bedroom community of Hayward.

Various private polls show that Brown has been picking up strength since the primary. He seems to have moved from dead even with Younger to an advantage of nearly 10 points. That would exceed his margin of victory in 1974, and give him a good boost for taking after Jimmy Carter in 1980.

Ironically, however, the campaign may cost Brown the special qualities, the aura of magic, that he would need to prevail in 1980. He has been obliged to show himself as the typical politico, wanting above all things to win. As he himself put it: "I'm a lot more traditional than people think."