The California governor's race will soon be tagged as the most expensive nonpresidential election in U.S. history, triggering a debate over money and influence that could emerge as the campaign's main issue.

Republican front-runner Meg Whitman, the billionaire former CEO of online auction house eBay Inc., will likely face off in November against Democrat Jerry Brown, a former governor and career politician supported by labour unions with many millions of dollars in serious contributions at their disposal.

The race so encloses itself at par with the $1 billion 2008 presidential contest. However, Whitman has said she is ready to spend $150 million to top the $148 million spent eight years ago in the New York gubernatorial election won by incumbent Republican George Pataki.

Whitman's benchmark is revealed to exceed that of billionaire New York Mayor Michael Bloomberg's 2009 $108 million self-funded campaign.

Whitman is revealed to have already divulged $39 million of her own funds into her campaign, while state Insurance Commissioner Steve Poizner, her sole competitor for the Republican nomination, has poured $19 million of his personal wealth into the race.