Bidding for conservative support on a popular Southern California talk radio show Tuesday, the three Republican candidates for the U.S. Senate traded barbs over taxes and who's best positioned to beat liberal incumbent Sen. Barbara Boxer in the fall.

The informal hourlong debate on KFI-AM 640's "The John and Ken Show" focused heavily on the candidates' records on taxes. And much of the fire was trained on the two leading contenders, former Congressman Tom Campbell and former Hewlett-Packard CEO Carly Fiorina, who at times have made exceptions to their stated anti-tax philosophies.

Fiorina was questioned by the third-place candidate, state Assemblyman Chuck DeVore of Orange County, about why she endorsed a ballot proposition in 2000 to lower the voting threshold needed to approve school bonds from two-thirds to a simple majority. Anti-tax groups opposed the measure, Proposition 26, which failed narrowly in a March 2000 election. (A similar measure lowering the vote threshold to 55 percent, Proposition 39, was approved by voters later that year.)

DeVore also noted that Fiorina, while at HP, spoke in favor of taxing Internet sales (in conjunction with broader reform of the tax system). He argued that those earlier positions are at odds with the campaign pledge Fiorina signed to oppose any new taxes.

"I'm looking for consistency," DeVore said. "Do you want people to follow through on their promises or do you want people who have a past record against Prop. 13?" he said, referring to the California law that requires a two-thirds vote to increase most taxes. DeVore also noted that after advocating for the school bond measure, Fiorina, who rarely has voted, failed to vote in the election in which it lost.

Fiorina brushed aside the criticism, noting that Proposition 26 had broad bipartisan backing as well as widespread support among the state's business leaders. The cause, school construction, was an important one, she added.

"Maybe it makes Chuck DeVore, who's sort of dog-paddling at 14 percent in the polls, maybe it makes him feel better to belittle other people's conservative credentials," Fiorina shot back.

Fiorina then turned the discussion to Campbell's endorsement last year of a package of temporary tax increases to balance the state budget, a proposal later rejected by voters.

Campbell responded that past Republican governors, including Pete Wilson and Ronald Reagan, were forced to resort to tax increases to deal with a crashing state budget. He also pointed out that he proposed spending cuts totaling three times the tax increases he supported.

Campbell then argued that his political profile is best suited to challenge Boxer, given the state's left-leaning electorate.

"If we're serious about replacing Barbara Boxer, we need to nominate somebody who is fiscally conservative and socially moderate," said Campbell, who favors abortion rights, gay marriage and some gun control measures.

Fiorina retorted that Campbell brought that philosophy to his two previous campaigns for Senate, in 1992 and 2000, to no avail.

"He used precisely the same argument both times — fiscally conservative, socially moderate — and lost resoundingly both times," Fiorina said. While Campbell lost a race against Sen. Dianne Feinstein in 2000 by 19 points, his defeat in the 1992 Republican Senate primary was by less than 3 points. Boxer went on to win the general election that year, and has been in the seat ever since.

Contact Mike Zapler at 202-662-8921.