Republican gubernatorial candidate Meg Whitman had hoped Saturday's debate in the heart of California's Central Valley would showcase her economic credentials and help siphon the support of independent and Hispanic votes away from Democrat Jerry Brown.

Instead, Whitman finds herself on the defensive and seeking to regain momentum with those voters after a tumultuous week in which she was forced to explain how she had an illegal immigrant housekeeper on the payroll for nine years and, according to her, didn't know it.

She also is addressing allegations from the housekeeper's attorney that she and her husband should have suspected the worker's status because of a Social Security Administration letter mailed to their home in 2003.

The billionaire former chief executive of eBay has worked hard to court independents and Hispanics, who are crucial to the campaign of any Republican running in a state in which Democrats hold a 13.4 percentage point edge among registered voters. She has trained a large share of her campaign account — $119 million of it from her personal fortune — on the Central Valley, which has been hit hard by the recession and is filled with communities where unemployment afflicts a quarter of the population or more.

The forced acknowledgment by Whitman and her husband this week that they fired Nicky Diaz Santillan when she confessed to being an illegal immigrant in June 2009 has thrown off Whitman's controlled campaign messages about reviving the economy, controlling state spending and reforming education as the candidates head into their second debate. The forum at California State University, Fresno is hosted by Spanish-language network Univision and targets a Hispanic audience.

Their first face-to-face exchange was Tuesday at the University of California, Davis, but the substance from that event was overwhelmed a day later when the housekeeper allegations surfaced.

Brown and Whitman sparred briefly over immigration during that first debate. Snatching a line from her Republican primary challenger, Steve Poizner, who had accused Whitman of being too soft on immigration, Whitman said then that California and other states need to turn off the magnet of jobs luring illegal workers to the state.

But that was before the allegations about Whitman's former housekeeper came to light and altered the dynamics of a race that two recent polls show is a dead heat.

Immigration issues are expected to play a much larger role in Saturday's debate, along with job creation, education and water supply issues that are a major concern for residents of the Central Valley.

Hispanics comprise 37 percent of the state's 38.6 million people and are expected to account for about 15 percent of voters on Nov. 2, according to a recent Field Poll.

Many of those voters are relatively new naturalized citizens who don't have any allegiance to a political party, representing a key opportunity for the Republican Party, said Harry Pachon, president of The Tomas Rivera Policy Institute at the University of Southern California.

Along with independents, who account for one in five registered California voters, Whitman has aggressively courted Hispanics with Spanish-language radio and television ads. That included spots during 15 games of the World Cup, as well as billboards and bus-stop posters.

A Public Policy Institute of California poll released this week showed Brown with only a slight lead over Whitman among Hispanic voters, but the survey was taken before the housekeeper controversy began dominating the race.

Brown and his supporters also are courting Hispanics, who typically vote Democratic but are being pursued heavily by Whitman.

The state's largest public employee union, the Service Employees International Union, is launching an ad campaign coinciding with Saturday's debate. It aims to keep the housekeeper controversy fresh in the minds of Hispanic voters.

The $5 million Spanish-language media campaign accuses Whitman of saying one thing in her Spanish-language campaign ads and another when she speaks in English.

Whitman also will likely be asked to explain a comment she made last month, when she unflatteringly compared Fresno to Detroit while discussing the poor economy.

"Fresno looks like Detroit. It's awful," she told the editorial board of the San Jose Mercury News.

California's unemployment rate is 12.4 percent, but it is much higher in many areas of the Central Valley, which has been hard hit by the foreclosure crisis and water shortages that have hurt the agriculture industry.