LOS ANGELES (AP)  -- Relishing their chance to finally play kingmaker, Californians went to the polls Tuesday in what could be record numbers for a primary election in which Republican and Democratic contests remained up for grabs.

The state offering the nation's richest trove of delegates grabbed last-minute attention from the campaigns of all the major candidates, just as state lawmakers hoped it would when they moved the presidential primary from June to February.

"The world is looking at California as a big player in the decision-making," Gov. Arnold Schwarzenegger told reporters Monday. "That's exactly what we intended."

Schwarzenegger appeared in Los Angeles for Republican Sen. John McCain of Arizona and at rallies for several initiatives on the ballot.

McCain and his GOP rival, former Massachusetts Gov. Mitt Romney, added last-minute California campaign stops on Monday.

Meanwhile, former President Bill Clinton traveled the state for a second straight day, stumping for New York Sen. Hillary Clinton, his wife, who is locked in a close race with Illinois Sen. Barack Obama in the Democratic primary.

The former president urged supporters at a Sacramento rally to get out the vote.

"All the surveys show, actually, there's still a fair amount of undecided people out there: People you can reach between now and tomorrow, people who can make a difference in this election," Clinton told a crowd of about 1,000 people at the state fairgrounds.

A weekend Field Poll showed nearly one in five Democratic voters and 15 percent of Republicans were still undecided.

California was one of 24 states holding primaries or caucuses on Tuesday but the spotlight was clearly on the nation's most populous state, where 370 Democratic and 170 Republican delegates are in play.

The excitement of this year's early primary appeared to have engaged voters. Registration hit a record for a presidential primary in California -- 15.7 million voters -- and a turnout of 55 percent was projected.

Nearly all the interest was generated by the close presidential contests.

"We're going to have a big influence on the election. We're the biggest delegate state, so that's exciting," said voter Kimberly Biddle, 42, a child development professor who lives in Rancho

Cordova.

Many Democrats were excited about the chance to choose between a woman and a black man.

In South Los Angeles, Dewayne Woodberry, 45, an insurance claims adjuster, said he voted for Obama.

"In order for minorities to get into office -- blacks or Latinos-- another minority has to be there," Woodberry said, adding that he also was influenced by Obama's emphasis on change.

Erendida Vargas, 32, a housekeeper, said she was eager to vote for Clinton, partly because she is a woman.

"She's great, and she is going to be the first woman president... Everything men do, we can do it, too," Vargas said.

Schwarzenegger appeared Monday with Democrats who support Proposition 93, a measure that would cut the number of years state lawmakers could serve in office from 14 years to 12 but allow them to spend all 12 in one house of the Legislature.

The change would allow 34 lawmakers who otherwise would be termed out of the Assembly or Senate this year to stay in office for another four or six years.

Weekend polls showed that measure slipping out of favor, while support was growing for a slate of gambling initiatives that would add up to 17,000 slot machines to four Southern California Indian casinos.

Schwarzenegger also campaigned on behalf of those deals. He signed the gaming compacts with the tribes and the Legislature approved them but opponents collected enough signatures to force a vote on propositions 94-97.

The gambling measures have attracted by far the most spending of any of the initiatives. The tribes and their allies raised $101 million to blanket the airwaves with commercials urging a yes vote.

About half of California voters were expected to vote with mail-in ballots.