LOS ANGELES (AP) -- California Republicans are struggling with the question of whether they should open their 2008 presidential primary to independent voters or restrict participation to the party faithful.

National GOP officials have been asked to review party rules to determine if California can consider opening its primary to 3 million independent voters.

Democrats permit independents to vote in their presidential primary. Some Republicans fear that if independents remain locked out of the GOP contest, they will be unlikely to vote for the Republican candidate in November.

California Republican primary voters have tended to be more conservative than the general electorate. Opening the primary to independents could enhance the prospects of former New York City mayor Rudy Giuliani and Arizona Sen. John McCain to capture some of California's 173 delegates, the largest stash of any state. Both candidates have been known to break with party orthodoxy and have demonstrated appeal that crosses party lines. (Related: Poll: Giuliani leads the GOP pack)

Longshot Republican presidential contender Jim Gilmore, a conservative former Virginia governor, has written to party leaders urging them to reject a "blatant attempt to manipulate the nomination process."

California legislators recently voted to move the state's presidential primary from June to Feb. 5 to bolster the state's influence. Gov. Arnold Schwarzenegger, a Republican, plans to sign the legislation.

There are 6.7 million Democrats in the state, or 42 percent of registered voters. Republicans make up 5.4 million, or 34 percent, and independents number 3 million, or 19 percent.