Inside Report (1)

Why are seven Republican candidates battling so hard for the Senate seat up for grabs next year in California? Sen. S. I. Hayakawa already holds the seat for the GOP, but recent polls show him running no better than fourth in a Republican primary. That leaves the field wide open for a candidate who's got the money and name recognition to take advantage.

Two candidates, Rep. Barry Goldwater Jr. and Maureen Reagan, are counting on their names for more than recognition. The First Daughter says she will appeal to her ''national constituency'' for funds. Goldwater Jr. hopes to benefit from a letter his father recently sent to 2.5 million conservatives across the US asking them to donate to his son's campaign.

One more attraction for the GOP candidate: Gov. Jerry Brown, the likely Democratic nominee, continues to slip in the California Poll. Only 32 percent think he would make an excellent or good senator.