San Francisco Mayor Gavin Newsom‘s move to open an exploratory committee to run for California governor in 2010 suggests a long, expensive and unpredictable campaign, according to experts who follow elections and campaign finance.

One of those experts said Newsom's announcement does have a financial calculation.

By going first, Newsom can rally donors and scare off other potential candidates, said Mark Petracca, chair of the political science department at the University of California, Irvine.

"It'll take him more time than it will Jerry Brown to introduce himself to voters," Petracca said.

In a state as big as California, that means making your name known through commercials, primarily on television. And that means money, Petracca said.

"He'll spend the next part of the year raising money, and he'll introduce himself to voters after that," Petracca said.

Starting a campaign means starting the pump for money, said Thad Kousser, a political science professor with the University of California, San Diego.

"What it really does is give him impunity to raise money between now and the end of the year," Kousser said.

That way, Newsom can also align himself with the forces battling Proposition 8, the initiative that would ban gay marriage in the state constitution, Kousser said. Newsom began offering gay marriage licenses in violation of state law in 2004.

"He's striking while the iron is hot," Kousser said.

Any money Newsom raises will be largely spent on name recognition because Newsom as a candidate is largely unknown outside the Bay Area.

To Southern California voters, Petracca said, Newsom is known as the mayor who flouted the law on gay marriages and little else.

Newsom has to define himself as something more substantial before a rival defines him negatively, Petracca said.

And to some extent, Newsom's fate could be tied to how Proposition 8 does in November, said another expert.

If the measure passes overwhelmingly, that could convince Democratic primary voters that Newsom would lose a general election governor's race, said Bob Stern, president of the Center for Governmental Studies, a nonprofit think tank in Los Angeles.

Experts said a trend to watch for will be self-financed candidates and how much they spend, if any step into the race.

Kousser and Stern both said that a self-financed candidate, such as former state Controller Steve Westly or Insurance Commissioner Steve Poizner, can break records for campaign spending if they begin dumping their own money into the race.

Kousser pointed to the 2006 Democratic primary, when Westly and then-Treasurer Phil Angelides spent more than $70 million combined, much of it Westly's own fortune.

"You need $10 million to $15 million to run a seriously primary campaign," Kousser said. "But I'm not sure that doubling that doubles your chances."

Experts agreed that more often than not, self-financed millionaire candidates in California get little for their spending.

Stern said a more intriguing trend will be how candidates take advantage of fund-raising through the Internet.

U.S. Sen. Barack Obama has proven in his presidential run that it's possible to raise millions that way from people outside traditional donation bases, Stern said.

But like Kousser, he said it's possible to overrate a war chest.

"It's spending, and spending wisely, not raising, that wins elections," Stern said.

ALSO on PolitickerCA.com:

• Newsom files papers to form exploratory committee for 2010 gubernatorial run

• Some candidates out-raising Newsom for 2010