SACRAMENTO, Calif. — California jolted the time-tested presidential primary schedule yesterday, moving up its 2008 contest to February 5 and setting the stage for a potentially decisive one-day, mega-primary across the country.

Governor Schwarzenegger signed legislation moving the state into make-or-break prominence from its position as a June straggler in the presidential nominating process.

“Now, California is important again in presidential nominating politics … and we will get the respect that California deserves,” Mr. Schwarzenegger said during a bill-signing ceremony.

California joins a handful of other states that have already scheduled February 5 primaries. But 15 other states — including Florida, Illinois, Michigan, New Jersey, New York, and Texas — are considering moving their contests to the same day.

Many strategists in both political parties believe it increases the significance of early successes in Iowa, New Hampshire, and South Carolina — all of which will hold contests before February 5.

“To go to California, you are going to need a huge head of steam,” Jenny Backus, a Democratic political consultant, said. “California moving up actually makes more attention go on the first lap. Even if you have all the money in the world, it will be hard to catch up to somebody who has racked up some victories in the first states.”