SACRAMENTO -- Gov. Jerry Brown continued his surge toward an unprecedented fourth term Tuesday, winning the primary for governor in a rout.

The big question of the night was which Republican candidate would finish second in the top-two primary, earning the right to take on the Democrats' Goliath in November and leaving an indelible mark on the future of the GOP in California.

Early returns showed former U.S. Treasury official Neel Kashkari narrowly leading Assemblyman Tim Donnelly by a few percentage points. Brown built an insurmountable lead immediately after the polls closed with support from more than half of voters.

Speaking to reporters outside the historic governor's mansion in Sacramento, Brown, 76, said he takes "nothing for granted" and will "campaign hard" against whichever Republican foe comes out on top.

"At this point, 40 years from the time I won my first primary for governor of California, I'm ready to tackle problems, not on a partisan basis, but on the long-term basis of building California and making sure we're ready for the future," Brown said.

Kashkari watched results roll in at the Port Theater in Corona Del Mar, while Donnelly stood by at the Hollywood Roosevelt Hotel in Los Angeles.

Representatives for their campaigns declined to comment on the early returns.

Brown's record as a responsible steward of the state's finances has drawn wide praise from voters across the political spectrum.

Kashkari, the former asset manager and Treasury official, pitched himself as a fiscal conservative with two simple goals: creating jobs and helping schools. In mailers and television ads, he axed a toy train to show his disapproval for Brown's high-speed rail project, which has lost public support.

Conservative Republican voters who identify with the tea party-favored Donnelly, an assemblyman and former Minuteman who once accused his Hindu opponent of promoting Shariah law.

He raised only a fraction of the campaign cash Kashkari took in, but he successfully cultivated an image as an outsider and underdog. Instead of recoiling, some voters cheered his status as a gun rights activist who was convicted of bringing a loaded gun to an airport in his carry-on luggage.

Whichever Republican prevails has even longer odds in November. In recent months, Brown clocked record-high approval ratings from a broad coalition of likely voters and won wide praise for helping to stabilize California's finances. He's also amassed a $20 million campaign war chest, of which he spent little leading up to the primary.

Contact Jessica Calefati at 916-441-2101. Follow her at Twitter.com/calefati. Read the Political Blotter at IBABuzz.com/politics.