Ronald Reagan is campaigning as if he still had an opponent. Sen. Edward M. Kennedy is behaving as if he still had a chance. And what used to be called "the super bowl of primaries" has this year been reduced to a political scrimmage in which the most important Democratic player did not appear.

With President Carter out of California and Republican George Bush out of the race, Tuesday's presidential primary has become an underfunded television battle between rival Kennedy and Carter commercials which emphasize the deep differences in the Democratic Party.

The most hard-hitting of these is a new Kennedy spot featuring actor Carroll O'Connor telling voters: "Carter equals Reagan equals Hoover equals Depression."

On the Republican side, interest has shifted to a Senate primary where seven candidates are vying for the dubious privilege of running against entrenched Democratic incumbent Alan Cranston in November. Former Los Angeles mayor Samuel W. Yorty and tax reformer Paul Gann have emerged as the leaders in a race considered too close to call.

Late last year some Democratic leaders in this state were worried that the 65-year-old Cranston, a physically fit former track star who looks older than his years, might be vulnerable of his age and liberalism.

Now, Cranston is virtually assured of an opponent older than he is and one so conservative that it should be possible for Cranston to capture the political center, as he did in two previous Senate campaigns.

At 70 Yorty is one of the few Republican candidates for major office anywhere who is older than the 69-year-old Reagan.It is Yorty's 19th campaign for public office and his fourth for the Senate, since he began his career in 1936 as a radical Democratic state assemblyman.

After discovering the issue of "communist infiltration" of state government, Yorty broke with the left wing of his own party but remained a Democrat through most of his career. As a House member, he was an advocate of a strong military defense and as a three-term mayor of Los Angeles was a big spender who favored expensive civic projects. Now, Yorty says that times have changed and government spending should be cut, except for the defense budget.

Because Yorty is much better known in populous Southern California, where until last December he hosted a television show, the former mayor is now a slight favorite over the 67-year-old Gann, a Sacramento businessman who in 1978 teamed with Howard Jarvis to give California the tax-cutting initiative known as Proposition 13.

Gann, a plodding and ungrammatical speaker who says that "We, the people, was sincere" in passing Proposition 13, is inarticulate on any issue except the antitax crusade. He holds a narrow 26 to 23 percent lead over Yorty in Mervin Field's latest California Poll, but his lead has shrunk each time a new survey has been taken and the trend seems to be in Yorty's direction.

A third Republican candidate, 49-year-old state Sen. John G. Schmitz, the American Independent Party president in 1972, has only 8 percent. However, Schmitz thinks he has a chance because of the abnormally high number -- 32 percent -- of undecided voters in the race, which has failed to generate noticeable enthusiasm for any candidate. The only relatively moderate candidate in the race, 41-year-old Pasadena attorney Ray Hanzlik, was unable to raise enough money to become competitive.

By the usual standards of California primaries, relatively little money is being spent, even on the presidential race.

Even before George Bush quit, the narrow tightrope which Reagan is walking in trying to stay within the federal spending limit had prompted a decision not to use advertising in California.

The Reagan campaign is relying on the efforts of scattered phone banks and a traditional flight tour of major California cities on Monday, the day before the election. In his campaign appearances here earlier this week before he left for Ohio, Reagan stuck to his standard speech with scarcely any reference to his new status as unopposed Republican candidate.

Sources in the Reagan campaign said this is a deliberate decision and that Reagan, in effect, plans to launch his general election campaign on primary night when he is expected to be a focus of national television coverage.

On the Democratic side, California continues to be at least superficially critical to Kennedy, who has acknowledged that he needs to win here in order to carry his campaign to the Democratic National Convention. But whether he wins or not, it is becoming increasingly apparent even to Kennedy supporters that Carter probably will win enough California delegates to be able to claim the nomination.

Kennedy will spend three of the last four days before the primary in California. His campaign will spend $195,000 on television advertising in Los Angeles, the San Francisco Bay area and Sacramento, using eight political commercials which range from "inspirational," pro-Kennedy spots to O'Connor's attack on Carter.

Carter, who doesn't plan to visit here, will counter with a $150,000 television campaign featuring man-in-the-street interviews critical of Kennedy.