Whatever he does, he says he won't be acting anymore, and he will be pushing environmental causes and clean energy.

So it's a bit ironic that he has not totally ruled out running for the U.S. Senate seat now held by three-term Democrat Barbara Boxer, the Senate's leading advocate of those very causes. As chairman of the Senate Environment and Public Works Committee, at last working with a President of her own party, a President who hosted the first fund-raiser of her 2010 campaign 14 months ago, Boxer is now positioned to do more for the environment and clean energy than anyone except President-elect Barack Obama.

Boxer Supposedly Vulnerable

But she knows her perpetual electoral status as one of the most liberal of senators: She's considered highly vulnerable every time she runs. And 2010 will be no exception.

Never mind that in successive campaigns she has beaten back onetime conservative icon Bruce Herschensohn; then whipped Matt Fong, the scion of the leading Asian-American political family in California, and most recently topped Bill Jones, a highly popular Secretary of State who has since become a successful businessman and promoter of ethanol in gasoline.

Despite that record, Boxer knows she'll be a decided underdog if Schwarzenegger goes after her seat.

"I'm getting ready for whatever happens, whoever runs," she chuckles. "It's always a tough race. So I've started lifting weights just in case it's Arnold. So far, I'm up to eight pounds."

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Boxer, unable to write herself copious campaign donations the way Schwarzenegger and other potential major 2010 players like Democrat Steve Westly and Republicans Steve Poizner and Meg Whitman can, has raised money steadily for more than a year.

Boxer, from the Inside

"I have to do this because I'm not rich," she says. "I think about how I'm going to win a race, no matter who it's against. We get ready in the same way each time. We'll do what it takes to raise the resources we need. We'll do the grass- roots. I love house parties. I love going to the smaller counties.

"We'll show people what we've done and can do."

One thing she can do is push causes far more effectively in concert with a Democratic President than any brand new junior senator could. Even a celebrity senator like Schwarzenegger would be.

Of course, that assumes Schwarzenegger can win a Republican primary election. He's never been in a contested one in his political career, winning office without any primary in the landmark recall election of 2003 and then taking the GOP's 2006 nomination without a serious contest because he was an incumbent.

Reasons for Opposing Arnold

But he has stirred the ire of the conservative Republicans at the core of the party in California by proposing higher taxes, producing deficit budgets and plumping for environmental causes including the fight against global warming, a phenomenon many on the right believe has nothing to do with human activity.

So if a substantial conservative ran against him — and one purpose of Schwarzenegger's always-large war chest is to scare off serious opposition within his own party — there is no guarantee Schwarzenegger would win. Especially with his positive rating running well under 50 percent in every recent poll and his record of frustration in handling the state's budget problems.

Still, it would not be smart to bet against him.

Which means that if Schwarzenegger is willing to settle for a junior role in the Senate and is ready to accept a post where he can't be boss, he will most likely be Boxer's opponent next year.

That would be a classic contest, a match of loud bombast against soft-spoken efficiency. A clash of political unbeatens, figures who never have lost an election. A campaign featuring two candidates who don't really need the job, one running for reasons of ego and a desire to ward off boredom, the other to retain a position of great influence on issues she cares about.

Great theater, for sure. And if it happens, certain to be the national headline event of the next mid-term election.