Obama vs. McCain + same-sex marriage = high turnout.
California's election equation is as simple as that.
The historic presidential race and emotionally charged ballot measure to ban same-sex marriage are expected to lure at least 76% of registered voters to the polls Tuesday, according to state election officials.
That is about the same turnout as the 2004 presidential election.
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But nearly 747,000 more Californians are registered to vote this time, meaning 13 million residents are expected to cast ballots -- up 410,000 from 2004.
In most Valley counties, turnout usually lags the statewide average. But a recent surge of voter registrations suggests rising enthusiasm.
An additional 35,274 central San Joaquin residents are registered to vote this year, compared with 2004. All five counties are projecting at least a 68% turnout. Fresno and Tulare counties are expecting 70% of voters to cast ballots.
To prepare, elections officials have ordered extra ballots.
"There's a great deal of interest, and we just don't want to be caught short," said Fresno County Clerk Victor Salazar.
The same-sex marriage measure will drive much of the turnout, especially in Republican-leaning regions such as the San Joaquin Valley, said Tony Quinn, a Sacramento-based political analyst. Proposition 8 would overturn a state Supreme Court decision this year that legalized same-sex marriage.
The latest Field Poll shows the measure falling six points short of passage, but 7% of voters still are undecided. In inland counties, the measure is drawing 57% support, compared with 39% on the coast.
Valley officials are advising voters to vote outside peak hours -- early morning and late afternoon -- to avoid waiting in line.
Still, no one is predicting the hours-long waits expected in some swing states. After all, California hasn't received much attention from the presidential campaigns, which have focused on more competitive states.
The latest Field Poll gives Democrat Barack Obama a 22-point lead over Republican John McCain in the state, which would be the largest victory margin by a presidential candidate in California since World War II.
But even with predictions of a California landslide, voters will show up in force -- especially Obama supporters, said Quinn, a former Republican legislative aide.
"If you're a supporter and you see [Obama] is going to win, you sort of have an inclination that ... 'I want to be there, too,' " he said.
Don't count out McCain, warned Fresno's Bill Jones, chairman of McCain's California campaign: "There's a huge amount of activity, and there's a lot of energy."
A lot of voters already have made their choices.
Forty-one percent of registered voters in California have requested a mail ballot, and nearly 18% of voters already have returned them or voted early in person, according to the California Association of Clerks and Elections Officials.
In the Valley, more than 127,000 voters already have cast ballots, or 17% of registered voters.
If you have a mail ballot but want to vote at the polls, bring your ballot with you. If you forget, you'll have to cast a provisional ballot, which won't be counted until officials verify that you haven't already voted by mail.
Another trend: Fewer electronic-voting machines.
California Secretary of State Debra Bowen last year put limits on touch-screen voting, drawing praise from electronic voting skeptics who feared the machines make voting systems susceptible to foul play.
On Tuesday, only two counties -- San Mateo and Orange -- will make extensive use of the machines.
Kings County, which used touch-screen voting in the 2006 general election, switched to paper balloting this year because the machine brand it was using did not meet Bowen's standards.
Now all ballots must will be driven to Hanford for counting, meaning a big chunk of the results might not be reported until midnight or later, said Ed Rose, the county's election manager.
"We're expecting an all-nighter," he said.