The latest field poll is a big deal for Fiorina. It is also a big deal for Boxer, though most of the attention has been on what the poll says about Boxer's negative numbers.
The polling numbers show Boxer's job approval rating has slipped since January. More voters now hold an unfavorable view of Boxer at 52 percent, compared with 41 percent favorable.
"This is really different than what we've seen in the past," says Mark DiCamillo, director of the field poll.
DiCamillo's done 43 polls on Boxer over the years. He says she is more vulnerable than ever before.
"Now she's trending negative. This is not a good time, this is her re-election year," says DiCamillo.
Fiorina's campaign is playing up Boxer's negatives.
"Fifty-two percent, which is extremely high, I think her highest ever. It really just shows Californians are not happy with her job performance," says Darcy Linn from the Fiorina campaign.
Boxer's campaign is playing them down.
"You know another key component of that poll is Boxer's strong support among independent voters," says Dan Newman from the Boxer campaign.
Independent voters are breaking for Boxer at 47 percent, compared to 39 percent for Fiorina. But ABC7's political analyst Bruce Cain says the real significance of this poll isn't Boxer's negatives, it's all about money.
"This helps Carly Fiorina because she can take these polling numbers to her donors and say, 'I have a chance to win this race, you need to invest in me.' If the numbers had been bad she wouldn't have been able to do this," says Cain.
Money is particularly important right now because of another field poll number: 36 percent of likely voters have no opinion of Fiorina and they don't know her. Cain says that's not surprising.
"Because the race that she ran was for a very small segment of the electorate, namely Republican primary voters," says Cain.
So Fiorina needs to define herself to that large pool of likely voters, but compared to Boxer, Fiorina's campaign is short of cash on hand to do that. She has just $620,000 at the end of May, compared to Boxer's $9.7 million.
"There's an opportunity here for Barbara Boxer to go on the attack and to define Carly Fiorina before she gets a chance to define herself," says Cain.
On Thursday, Vice President Joe Biden headlined a fundraiser for Boxer in Atherton. About 200 guests raised a total of $300,000. On Friday, he was with Boxer at another big money event in Los Angeles.
Fiorina does have a large personal fortune; she put $5.5 million of her own money into her primary campaign. So we'll be watching to see how much more Fiorina is willing to spend, whether or not her donations increase after this poll, and whether Boxer's campaign will seize this opportunity.
Four months out, this holds the potential of being a pivotal moment in the race.
