GARDENA, Calif. -- Bill Clinton headed to Orange County, Stockton and Sacramento on Monday to energize his wife's slipping campaign, a day after Barack Obama picked up Maria Shriver's endorsement and Oprah Winfrey urged women to look beyond gender in the neck-and-neck California Democratic presidential primary.

California's crucial role in the Super Tuesday primaries was evident as the former president scheduled a second day of last-minute campaigning here. He spent Sunday in black churches in the Los Angeles area to rally support for his wife.

A new voter survey showed the state race a dead heat between the former first lady and the Illinois senator, a sign that the big lead Clinton had held for months withered away.

At stake in Tuesday's primary are 370 Democratic delegates, and more than half the voters are expected to be women.

On Sunday in Los Angeles, Winfrey told 9,000 people at a rally that "I'm just following my own truth, and that truth has led me to Barack Obama."

She urged women to "decide for yourself what to do" -- an obvious appeal to steal votes for Obama from a voter group Clinton has long expected would be in her column.

None of the three top Republican candidates personally campaigned Sunday in California, where 170 delegates are in play and Arizona Sen. John McCain has been leading in polls.

Instead, candidates relied on volunteers to make thousands of phone calls and knock on doors to bring out supporters.

Former Massachusetts Gov. Mitt Romney was alone among Republicans airing TV commercials in the state. His supporters warned conservatives that a vote for former Arkansas Gov. Mike Huckabee could tilt the race to McCain.

Just over a week after Obama routed Clinton in the racially charged South Carolina primary, her husband delivered a low-key speech Sunday to black parishioners at a Gardena church that avoided any direct criticism of her rival. After his sharp-elbowed campaigning in South Carolina, the former president never mentioned Obama's name and said at one point, "I'm not against anybody."

"For many of us who have waited a lifetime to see America break race barriers and gender barriers, it seems such a cruel irony that we have an embarrassment of riches in this election. I like all the people who ran for president on our side," he said at City of Refuge church.

Winfrey appeared Sunday with Caroline Kennedy, the daughter of former President John F. Kennedy, and Obama's wife, Michelle.

The crowd at Pauley Pavilion on the University of California, Los Angeles, campus also got a surprise visit from Shriver. She endorsed Obama, calling him as inspirational and innovative as the state itself.

Winfrey appealed to women voters, saying they shouldn't feel guilty if they decided not to vote for the first female candidate with a real shot at the presidency.

An independent Field Poll released Sunday showed Clinton's long-standing advantage over Obama had evaporated. The race is now a dead heat, with Clinton at 36 percent and Obama at 34 percent among likely Democratic primary voters.

In mid-January, Clinton held a 12-point edge. The poll also found that 18 percent of voters remain undecided, making a last-minute campaign push all the more crucial.

Among Republicans, Sunday's Field Poll showed McCain with an 8-point lead over Romney, 32 percent to 24 percent. Huckabee had the support of 13 percent of likely voters, with 15 percent undecided.