LOS ANGELES -- If the future happens first in California, the Republican Party has a problem.

The most populous U.S. state -- home to 1 in 8 Americans -- has entered a period of Democratic political control so far-reaching that the dwindling number of Republicans in the Legislature are in danger of becoming mere spectators at the statehouse.

Democrats hold the governorship and every other statewide office. They gained even more ground in Tuesday's elections, picking up at least three congressional seats while votes continue to be counted in two other tight races -- in one upset, Democrat Raul Ruiz, a Harvard-educated physician who mobilized a district's growing swath of Hispanic voters, pushed out longtime Republican Rep. Mary Bono Mack.

The party also secured a supermajority in one, and possibly both, chambers of the state Legislature.

"Republican leaders should look at California and shudder," says Steve Schmidt, who managed John McCain's 2008 campaign and anchored former Republican Gov. Arnold Schwarzenegger's re-election team in 2006. "The two-party system has collapsed."

Republican voter registration has dipped so low -- less than 30 per cent -- that the party's future state candidates will be hobbled from the start.

Republicans searching for a new direction after Mitt Romney's defeat will inevitably examine why President Barack Obama rolled up more than 70 per cent of the Hispanic and Asian vote, and 9 of 10 votes among blacks, essential ingredients in his victory. Women also supported Obama over Romney nationally and in California, where they broke for the president by 27 percentage points.

There is no better place to witness how demographic shifts have shaped elections than in California, the home turf of Richard Nixon and Ronald Reagan that just a generation ago was a reliably Republican state in presidential contests.

A surge in immigrants transformed the state, and its voting patterns. The number of Hispanics, blacks and Asians combined has outnumbered whites since 1998 in California, and by 2020 the Hispanic population alone is expected to top that of whites. With Latinos, for example, voter surveys show they've overwhelmingly favoured Democratic presidential candidates for decades. Similar shifts are taking place across the U.S.

"There are demographic changes in the American electorate that we saw significantly, first, here in California and Republicans nationally are not reacting to them," said Jim Brulte, a former Republican leader in the California Senate.

"Romney overwhelmingly carried the white vote -- 20 years ago, that would have meant an electoral landslide. Instead, he lost by 2 million votes" in the state, Brulte said.

Perhaps no part of the state better illustrates how Republicans have surrendered ground than in Orange County, once a largely white, Republican bastion where Nixon's seaside home became known as the Western White House.

Today, whites make up a little more than 40 per cent of the population, while 2 in 10 residents are Asian and about 1 in 3 is Hispanic, according to the census.

In 1980, Jimmy Carter managed to collect about a quarter of the vote against Reagan in Orange County. But by 1996, with the county diversifying, Bill Clinton grabbed 38 per cent of the vote, and Al Gore boosted that to 40 per cent in 2000. This year, Obama won 44 per cent of the vote in Orange County, according to preliminary returns.

Romney "implemented a winning election strategy for 1980," University of Southern California professor Patrick James said in a statement issued by the school. "If you look at the demographics and voting proportions, the Reagan coalition would not win a majority today."

Celeste Greig, president of the conservative California Republican Assembly, said in an email to supporters Friday that the party was in need of a makeover, emphasizing Main Street over Wall Street.

"We have to admit that as a party in California, we're just plain disorganized," she wrote.

Romney bypassed California this year except for fundraising events, waging his fight in battleground states such as Ohio and Florida. In claiming the biggest electoral prize in America, California's 55 electoral votes, Obama rolled up a nearly 21 percentage point margin. Voters also returned Democratic Sen. Dianne Feinstein to Washington in a landslide, after Republicans put up a virtually unknown candidate, Elizabeth Emken, an autism activist who had never held elected office.

Independents now outnumber Republicans in 13 congressional districts in California, a trend analysts predict will continue.

California counted more registered Republicans in 1988 than it does today, although the population has grown by about 10 million over that time. You'd have to go back to that year to find a Republican presidential candidate who carried the state, George H.W. Bush.

Surprisingly, Democrats continued to make gains in the state even at a time of high unemployment, with polls showing that voters are unhappy with Sacramento and Washington. And it could get worse for the Republicans who are trailing in two other House races in which the vote counting continues.

It remains unclear what direction Democrats, who have close ties to public employee unions, will take with their additional clout. If they achieve the supermajority in both houses of the Legislature, Democrats can pass tax increases and override gubernatorial vetoes without any Republican support.

The state is saddled with a litany of problems, including a long-running budget crisis, massive, unfunded public pension obligations, tuition increases at California universities and growing demands for water, affordable housing and energy.

Gov. Jerry Brown sounded a cautionary note this week, saying he intended to avoid spending binges.

Still, Democrats believe they have the state's demographics on their side with a message that appeals to a younger, more diverse population.

More than half the young voters in the state, ages 18 to 39, are Hispanic, according to the independent Field Poll. Thirty-five per cent are Asian. If you look into a classroom in the Los Angeles area -- tomorrow's voters -- 3 of 4 kids are Hispanic.

The Republicans retain pockets of influence regionally, including rural, inland areas.

Republican National Committee member Shawn Steel has been pushing the party to become more aggressive about recruiting Asians.

"It's not just all about the Latinos," he says.

Schmidt traces Republican troubles with Hispanics to 1994, when voters with encouragement from Republican Gov. Pete Wilson enacted Proposition 187, which prohibited illegal immigrants from using health care, education or other social services.

The law eventually was overturned, but it left lingering resentment with many Hispanics at a time when the Latino population was growing swiftly and becoming increasingly important in elections.

California "is not just a large state, population-wise, it's a trend-setting state," said Schmidt, a public relations strategist. "It could be a glimpse of the future."