The likely victory of Gov. Arnold Schwarzenegger in next month’s election could change the dynamics of California government and the way both national parties think about this mega-state.

It has been a long time since any Republican presidential candidate won California – not since George H.W. Bush in 1988. And it has been almost as long since any Republican won major statewide office – until Schwarzenegger won in the special election of 2003.

But the circumstances of that race were so odd – a referendum on the unpopular incumbent, Democrat Gray Davis, and a free-for-all among dozens of would-be successors running virtually without party support – that Schwarzenegger’s victory seemed almost happenstance.

But now he is running as the Republican nominee against a single legitimate Democratic contender, state Treasurer Phil Angelides, a former party chairman. And the double-digit lead Schwarzenegger has fashioned cannot be put down to luck.

Rather, it reflects his rapid adaptation after a serious political miscalculation. In 2005, he declared war on the Democratic Legislature and the public employee unions and forced a special election on four initiatives designed to cripple the unions’ influence and strengthen his hand as governor. Voters rejected all of them and drove his approval scores into the basement.

But after that repudiation, Schwarzenegger this year reopened negotiations with the Legislature, passed a heap of big bills, and won the applause of an independent electorate.

To be sure, there are still skeptics who argue that the governor has no convictions and therefore is totally unreliable. In his political biography, “The People’s Machine: Arnold Schwarzenegger and the Rise of Blockbuster Democracy,” author Joe Mathews quotes the judgment of bodybuilder Rick Wayne, a buddy of the governor. “I’ve never known Arnold to be a conservative,” Wayne said. “I’ve known Arnold to be a chameleon.”

Some Democratic lobbyists in Sacramento expect a re-elected Schwarzenegger to go back to union-bashing and fighting with the Legislature. But his aides and intimates think that is a misreading of the man and the state. Both, they say, are firmly rooted in the center of the political spectrum.

Indeed, key Republicans here – including some of George W. Bush’s former people imported for the Schwarzenegger campaign – think the governor’s example is one that could be emulated in 2008.

Their argument is that at least three possible Republican contenders – Rudy Giuliani, the former mayor of New York, John McCain, the senator from Arizona, and Mitt Romney, the governor of Massachusetts – could compete effectively for California if they made the effort.

To have a chance, they would have to abandon the Republican habit of treating California as a piggybank – a place to fly in, pick up a bundle of cash, and fly out.

They would not have to go as far as Schwarzenegger has in embracing Democratic issues. The state might respond to a candidate who simply combines fiscal prudence and avoidance of higher taxes with a progressive attitude on the environment and such social issues as immigration and civil rights.

Underlining this belief is a new report from Mark Baldassare, the respected pollster of the nonpartisan Public Policy Institute of California, highlighting the different characteristics of California voters and nonvoters.

As the state’s population has swelled, with immigration and natural growth, the percentage of people going to the polls has shrunk. The majority of those who vote regularly now in California are over 45, own their own homes, have college degrees and enjoy household incomes of $60,000 per year or more. By contrast, the majority of nonvoters are younger, poorer, less educated renters.

Because Republicans have abandoned California politics for so long, Democrats have been allowed to dominate the state. If its rich hoard of 55 electoral votes becomes competitive for 2008, it would be a boon to both parties. Democrats would still have a substantial advantage, with their support for abortion rights and appeal to working families and minority groups. But moderate Republicans could also compete and challenge and thereby shift the focus of the entire national election toward the political center.

All that – and more – is implicit in Schwarzenegger’s run this year, making it potentially the most significant Republican victory in what otherwise looks like a year of Democratic gains.