Inside, it was even hotter, with sharp, heated exchange.
The three-term Democrat on how the former Hewlett-Packard CEO performed: "We know she shipped jobs overseas, thousands of them. We know she fired workers, tens of thousands of them," said Boxer.
Seizing the anti-incumbent sentiment among voters, Fiorina hit home how Democrats have made a mess of things.
"In 20 months alone, our unemployment rate went from 10.2 percent to 12.3 percent," said Fiorina. "Our debt has grown from $10.8 trillion to $13 trillion, and on its way to 20 trillion."
On the hot button issue of Proposition 8, the voter-approved initiative banning same sex marriages, the two clearly were polar opposites.
"When voters have such a clear decision, for that clear decision to be overturned by a single judge seems perhaps inappropriate," said Fiorina.
"The only way to get equal rights to gays and lesbians is to say that there should be marriage equality," said Boxer.
The candidates had a chance to attract Latino votes on immigration issues.
Fiorina declared her support for the Development, Relief and Education of Alien Minors (DREAM) Act, a path for citizenship for kids who came to the United States illegally. But she toed the conservative line for undocumented adults.
"Let me say, I don't think there should be amnesty for those who came here illegally," said Fiorina.
"The way to get this economy going is to go with comprehensive immigration reform," said Boxer.
Independent voters are also key to winning elections in California. Both women had to come closer to the middle. The latest Rasmussen Report poll pegs this race as dead even, but the fundraising advantage goes to Boxer, 12 to 1.