[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/07/08/art.boxer.gi.jpg caption ="A new Field Poll shows California Democratic Senator Barbara Boxer is still facing a tough reelection battle."]
(CNN) - Hours before Vice President Joe Biden headlines a fundraiser in California for Sen. Barbara Boxer, a new survey indicates that the race between the three-term Democrat and Carly Fiorina, her Republican challenger, remains tight.
According to a Field Poll released Thursday morning, 47 percent of California voters say they support Boxer, with 44 percent saying they back Fiorina, and nine percent undecided. Boxer's three point advantage is within the survey's sampling error.
The poll indicates that Boxer leads by eight points among crucial independent voters.
Fiorina, the former Hewlett Packard CEO, who was also an economic adviser and surrogate for Sen. John McCain's White House bid, beat out two other rivals in the GOP primary earlier this month.
Boxer led Fiorina by 4 points in a Reuters/Ipsos poll late last month, the only other non-partisan survey conducted since the June 8 primary.
According to the Field Poll, 42 percent approve of the job Boxer's doing in the Senate, with 43 percent saying they disapprove. And her unfavorable rating now stands at 52 percent.
The survey indicates that more Californians are now familiar with Fiorina. Nearly two in three voters in the Golden State can now offer an opinion of her, nearly double the level of people familiar with her in January.
Biden headlines a fundraiser for Boxer Thursday evening in Atherton, California. President Barack Obama traveled to California twice this year to help raise campaign funds for Boxer.
Earlier in the day, the vice president is the main attraction at a campaign event in Oregon for Rep. Kurt Schrader, who faces a tough re-election battle.
The Field Poll was conducted June 22-July 5, with 1,005 California voters questioned by telephone. The survey's overall sampling error is plus or minus 3.2 percentage points.
Follow Paul Steinhauser on Twitter: @psteinhausercnn