Boxer, who authored a bill in 2002 allowing commercial airline pilots to carry guns in cockpits, says Fiorina supports selling guns to people on the government's "no-fly list," which is designed to keep terrorists off planes.
"It's a choice between someone who's working to keep our airlines safe and working to keep guns out of the hands of terrorists, versus someone who believes that those on the suspected terrorist no-fly list should be able to buy a gun. Any gun," said Boxer.
"Barbara Boxer knows perfectly well the difference between the terrorist watch list and the no-fly list. And if she doesn't know the difference, then that's really a problem," said Fiorina.
Fiorina says Boxer is once again trying to distract voters from the most important issue: jobs.
Speaking Monday at an auto dealership in San Bernardino, where several dealers have gone out of business, Fiorina, the former Hewlett-Packard CEO, pointed to that county's unemployment rate, which has risen from 12.4 percent when the federal stimulus bill was passed in February 2009, to 14.9 percent today.
"Senator Boxer, taxing, spending, regulating and borrowing is not working. It is failing," said Fiorina. "This election is about jobs. This election is about out-of-control government spending. This election is about the voters of California saying, 'You know what, we need to grow jobs. We need to hold Washington accountable.'"
The incumbent senator countered by citing Fiorina's record, which includes laying off 30,000 employees.
"My opponent is running on her record at Hewlett-Packard, where, as I've said numerous times because that is her only record, she was fired, named one of the worst CEOs by five publications. I've won 10 elections," said Boxer.
With this being a close race and California a critical state, high-profile Democrats and Republicans have been coming west. Former President Bill Clinton and Sarah Palin have all recently visited the state to campaign for candidates. Friday, President Barack Obama will be at USC to stump for Boxer.
This weekend, John McCain was in San Diego stumping for Fiorina when he took to the kind of personal swipe at Boxer almost never seen among Senators.
"Barbara Boxer is the most bitterly partisan, the most anti-defense Senator in the U.S. Senate today," McCain said. "I know that because I have had the unpleasant experience of having to serve with her."
The harshness of the attack seemed to surprise even Fiorina.