Going into the 1964 election, CA had two senators: the liberal Republican Thomas Kuchel and the Democrat Clair Engle. Kuchel was not up for re-election until 1968 and Engle, battling brain cancer since 1963 and partially disabled, was retiring his seat at the end of 1964. The national Democratic Party got to work and airlifted JFK's and LBJ's Press Secretary Pierre Salinger back to his home turf from which he'd never run for or held public office. In the primary, he ran against and defeated the twice elected CA State Controller Alan Cranston..
Senator Engle died on July 30,1964, and Gov. Pat Brown appointed Salinger to that Senate seat for the remainder of the term which also allowed Salinger to run in the general election as the incumbent Senator. That November, as LBJ was winning a landslide of historic proportions, Salinger lost to the washed up song and dance man, George Murphy.
Murphy was enough of an embarrassment as a Senator that in 1970 he lost in the general election to the Democrat John Tunney, son of boxing champion Gene Tunney and college roommate of Edward Kennedy. Tunney lost his 1976 reelection bid to S.I. Hayakawa The Republican Party wisely dumped him after one term and went with Pete Wilson in 1982 and he defeated the outgoing Governor and Democratic Senate Nominee Jerry Brown in that general election. Wilson was elected Governor in 1990 (defeating Dianne Feinstein) and appointed John Seymour to his Senate seat. In the special election in 1992 Seymour lost to Dianne Feinstein. That's seven different people in a single US Senate seat in three decades. There is such a thing as too much change. (Feinstein may not be a good Senator, but voters think she's better than the revolving door that came before.)
But I want to go back to 1964. California was governable at that time. Governor Pat Brown was well regarded. And LBJ beat Goldwater by an 18.32 margin in CA, only two points less than the national margin. There was no political reason why a Republican, much less a novice, should have won Engle's Senate in 1964. Except for Democrats shooting themselves in the foot. If Salinger had not been selected by someone in the higher echelons to return to California to begin his career in elected office with the US Senate, Alan Cranston would have been the Democratic nominee* and he would have been elected (as he was in 1968 when the GOP dumped Kuchel in favor of a Reaganite with an ugly face). George Murphy's success also set the stage for Ronald Reagan to take on Pat Brown (the man who defeated Richard Nixon in 1962) in the 1966 gubernatorial election. And the rest, as they say, is history.
*Democratic primary voters shouldn't be left off the hook. They could have nominated Cranston in 1964. They could also have nominated George Brown, Jr. in 1970 instead of Tunney. George Brown would have been an excellent Senator and not a one-term wonder like Tunney, but on this, I'm not impartial because I did door-to-door canvassing for Brown.