Gov. Scott McCallum and his opponent in the gubernatorial race, Attorney General Jim Doyle, clashed during a debate Wednesday over taxes and the state's fiscal problems.

Doyle blamed McCallum for much of the $2.8 billion deficit the state could face in the upcoming two-year budget, while McCallum charged that Doyle's promises would double the shortfall.

McCallum said tax increases were not inevitable, and cited the plan he signed this summer to fix a $1.1 billion budget deficit caused by falling revenues due to the recession.

"Taxes are directly related to jobs,'' he said. "Raising taxes drives out jobs.''

Doyle said McCallum's plan required the state to use all its money from a settlement with tobacco companies to balance the budget.

"He cashed in every dime of the tobacco money,'' Doyle said, calling it "a one-year payoff just to get through this election.''

McCallum accepted a challenge from Doyle to stop running negative ads — but only if Doyle stopped running his first. Doyle said afterward he would not.

It was the first state gubernatorial debate that included two third-party candidates. Libertarian Ed Thompson said he didn't mind the negative campaigning by the major-party candidates.

"It saves me a lot of money,'' he said. "Keep it up guys, you're doing a great job.''

Meanwhile, the state's ethics board said Wednesday it would investigate charges that McCallum and Doyle improperly used state airplanes.

The candidates have accused each other during the campaign of using the planes for personal or campaign-related trips, which state officials say should be either fully or partially reimbursed.

State records show McCallum has made 277 state flights since taking office, and that Doyle used state planes 40 times between 1998 and 2001.