Bet on the donkey in this race

Now that both parties have candidates running for governor, Californians are sure to hear a bit of conventional wisdom about state politics: Voters typically elect Democrats to the Legislature but Republicans to the governorship.

Like so much conventional wisdom, it’s dead wrong, or at least seriously misleading.

For the last 15 years, California voters have, for good or ill, shown a remarkably consistent preference for Democrats. Sure, we have a Republican governor, but that says more about Arnold Schwarzenegger -- he is an exception to almost every rule -- than it does about the GOP generally.

The fact is that as a Democrat, Jerry Brown starts with a big built-in advantage in his back-to-the-future search for his old job.

Exhibit A in the conventional wisdom view is that Republicans have held the governor’s office for 23 of the last 28 years, the only exception being the bobtailed tenure of Democrat Gray Davis.

That’s true, but the measurement reaches too far back in the state’s political history. In the 1980s and early ‘90s, Californians elected Republicans George Deukmejian and Pete Wilson as governor, but they chose Republicans in lots of other races as well.

Both Ronald Reagan and George H.W. Bush carried the state in presidential contests -- unimaginable for a Republican now -- and Wilson won election to the U.S. Senate twice. As late as 1994, Republicans won offices up and down the ballot and even captured a majority of seats in the Assembly -- though Willie Brown’s wizardry temporarily foiled them from taking control of the chamber.

In the ‘80s and early ‘90s, in other words, California voters elected Republicans to many jobs, not just the governorship.

That was then. Starting with the 1996 election, statewide winners have been almost all Democrats.

If you want a set of numbers to illustrate the partisan status of California politics, it’s not 23 of 28 years -- the Republican run in the governor’s office -- it’s 25 of 30 elections. In the last 15 years, Californians have voted for statewide or national candidates for partisan office 30 times. Democrats have won 25 of those elections.

Schwarzenegger’s occupancy of the capital’s key office since 2003 just shows the unusual nature of his career. Not only is he a global celebrity, he initially was elected governor during the wild-ride recall of Davis, which meant that Schwarzenegger never had to win a Republican primary. That allowed him to avoid the rightward lurch required of most GOP candidates as they try to win over the party’s conservative base.

In fact, strip away the recall election and the cases of Republican incumbents winning re- election (including Schwarzenegger in 2006), and only once in 15 years have California voters chosen a non-incumbent Republican: Steve Poizner’s victory as insurance commissioner four years ago.

Democratic dominance should hardly be surprising. Republican registration in California is at an all-time low -- 31% -- and many of the so-called independents are in fact Democrats who just won’t come out of the nonpartisan closet. (We know this because they tell pollsters that they lean toward the Democrats.)

What’s more, research by UC San Diego political scientist Gary Jacobson shows that Californians have been growing more consistent in their partisan preferences. The percentage of voters splitting their ticket between the two parties declined sharply from the 1970s through the 1990s, just as the state achieved its new level of Democratic purity.

More and more, California voters are Democrats who vote for Democrats.

Does this guarantee a Brown victory in November? Not at all. Meg Whitman and Poizner could mount self-financed airwave blitzes that overwhelm the campaign. Anger over the economy and dissatisfaction with President Obama could hamstring Democrats. Brown could end up smelling like the political equivalent of 35-year-old fish.

But I doubt it. By and large, elections are decided not by campaigns but by the underlying structure of the electorate.

Barack Obama won the presidency last year not because he gave eloquent speeches and ran a smart, effective campaign -- he did both -- but because people were fed up with George W. Bush, a horrendous economy and an unremitting war in Iraq. Any plausible Democrat would have won.

I suspect the same thing is true in this year’s governor’s race. Californians have consistently hunkered down in the Democratic column for a decade and a half now, and any statewide Democratic candidate starts with a huge advantage -- even a septuagenarian moonbeam.

Ethan Rarick is the director of the Robert T. Matsui Center for Politics and Public Service at UC Berkeley and the author of “California Rising: The Life and Times of Pat Brown.”