When the votes are counted on Tuesday night in California, Democrats will easily sweep the top contests. Senator Barbara Boxer is likely to defeat challenger Carly Fiorina, 51-46 percent (Nate Silver’s projection at 538.com), and last week’s California Field poll shows Democrat Jerry Brown ahead of Republican Meg Whitman in the gubernatorial race by ten points.

Across the nation, the Republicans have a better-than-even chance of winning fifty seats held by Democrats—but none of those seats are in California.

Why are the Republicans doing so badly in California, when they are anticipating sweeping victories so many other places? 

It’s not "the economy, stupid." Yes, the rule in politics is that the unemployment rate is the most powerful predictor of incumbent approval ratings. But that’s not true in California, which has the third-highest unemployment rate in the nation—officially 12.4 percent (while the nation as a whole is at 9.2 percent).

It’s not campaign funding. Yes, the rule in politics is that the candidate with the most money wins. But Whitman has spent $141 million on her campaign, outspending Brown four to one.

It’s not the candidates. Yes, Whitman looks weak now. But just a month ago she was tied with Brown. And Boxer was considered "beatable" a few months ago, when her disapproval ratings were slightly higher than her approval ratings.

The best explanation: Democrats remain strong in California because "demography is destiny." That’s what Harold Meyerson says—he writes a column for the op-ed pages of the Washington Post and the LA Times

"The electorate in California is the least white of any state, except Hawaii," Meyerson said in a recent interview. "That matters, because the Republicans have a genius for alienating voters of color."

The Republican Party is increasingly a party of white people—and that, Meyerson says, "is death in California." And although the Democrats in Congress have been, frankly, bad on immigration reform, the Republicans have been a lot worse: for them, "you’re a criminal suspect if you look Latino."

The only Republican to win a top statewide office in California in the past fifteen years is Arnold Schwarzenegger, and the only reason he won was that he didn’t have to run in a Republican primary—he won the recall vote against Democrat Grey Davis in 2003. Republican primaries compel Republican candidates to move to the right—and, Meyerson says, "to say things that are a disaster with the Latino community."

California is exceptional also because the share of workers who are white and working class is much lower than the share in the Midwestern states, where the Democrats face big losses. While Obama has "a low cultural affinity with those voters," Meyerson says, the way to reach them has been through an economic appeal—but there has not been enough in the Obama economic program to convince those voters that he is their economic champion. 

In the past, unions made the case to their members that the Republicans would be worse—but in the private sector union membership is down to 7 percent of the work force, so the Democrats don’t have much to push back with. But in California, unions are stronger than most other states.

The big change began in the early 1990s, when aerospace collapsed in California. That led to a major out-migration of the white working class. At the same time there was a major in-migration of Latinos. 

The result is that, in the last four years the Democrats have addded a million new voters in California, while the Repulicans have lost 200,000. As of September 3, the official count lists 44 percent of the state’s registered voters as Democrats, while only 31 percent were Republicans. So the GOP will be celebrating in a lot of states on Tuesday night, but not in California.