Back in the day, when California was a purple state whose major offices could be won by either party, Republicans loved "the fishhook."

It was so named for how the dependably Republican counties looked on a state map – an unbroken north-south string of inland counties that hooked into San Diego and Orange counties in Southern California.

During the 1980s and into the 1990s, Republican candidates for president, senator or governor could depend on running up big fishhook margins to offset the equally large advantage that Democrats held in the San Francisco Bay Area.

Republicans won most of those top-of-the-ticket races during that period by exploiting the fishhook, but it also depended on another factor – the relative neutrality of Los Angeles County, home to a quarter of the state's voters.

Democrats usually won Los Angeles, but only by small margins. If the Republicans' fishhook totals, especially in San Diego and Orange counties, were big enough, they could triumph in statewide contests.

Despite high levels of population growth and strong Republican margins in the fishhook counties, the strategy began to fade in the 1990s because Los Angeles County began shifting from virtual neutrality into a very strong pro-Democrat posture, thereby tilting the entire state.

What happened in Los Angeles?

Yours truly researched that question in great depth a few years ago for a chapter of a book titled "The New Political Geography of California."

The end of the Cold War is what happened.

Southern California's defense industry was clobbered by the end of a nearly half-century-long standoff with the Soviet Union in the early 1990s. The result was a sharp recession and a massive migration, mostly of aerospace workers and their families, from the state.

These Republican-leaning aerospace workers took their votes with them, while a burgeoning union movement in Los Angeles generated a surge of Latino voting that transformed the region politically and shifted it into the Democratic column.

The fishhook reappeared for one election in 2006. With Los Angeles neutral, Republican Arnold Schwarzenegger defeated Phil Angelides to win a second term as governor.

This month's election, in which Democrats won almost everything, underscored the demise of the fishhook.

Not only did Los Angeles County give President Barack Obama a million-vote-plus victory over Republican Mitt Romney, but three of the largest fishhook counties – San Diego, Riverside and San Bernardino – voted for the president.

To put it another way, even if Los Angeles had returned to its old neutrality, Obama would have won by about a million votes in California.

The Republican fishhook, it could be said, lost its barb.

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Dan Walters

Order Reprint