"If you want four more years of Ed Rendell-like policies, then I would select my opponent," Corbett, the state attorney general, said at the last of three gubernatorial debates.
"He wishes he was running against Ed Rendell," retorted Onorato, who touted his seven-year record as the elected executive of Allegheny County as evidence of his ability to hold the line on taxes and reform government.
Rendell, a Democrat, is stepping down in January, after completing the maximum two terms as governor.
Onorato chided Corbett for modifying his no-new-taxes pledge in the previous debate, held Saturday night in Pittsburgh, to rule out increases in fees or other levies, including a prospective increase in employees' contributions to the state unemployment fund to help pay down a $3 billion debt to the federal government.
Corbett had initially raised the possible employees' increase - while opposing a corresponding increase in employers' share - in the first debate, which was staged at a Pennsylvania Chamber of Commerce dinner in late September.
"You can't change your answer depending on what audience you're talking to," Onorato told his opponent. Corbett said he had taken time to consider about the issue and had changed his mind.
The candidates also clashed over a proposed tax on the state's burgeoning natural gas industry.
Onorato said Pennsylvania should follow the lead of other gas-producing states and tax the gas being extracted from the rich Marcellus Shale reserve to finance environmental protection.
"This is no time to take an extreme position like Tom's taking and make Pennsylvania the only state that doesn't have a severance tax," he said.
Corbett said a tax would "chase away" a young industry that is expected to create thousands of sorely needed jobs in Pennsylvania.
"We are the Saudi Arabia of natural gas if we develop it and develop it now," he said.
Onorato said Corbett's refusal to impose a tax stems from loyalty to an industry that has contributed more than $350,000 to his campaign since the beginning of the year.
"You're jeopardizing the taxpayers, and you're jeopardizing the environment," Onorato said.
Corbett said he is as concerned as anyone about the environment.
"I will never put the profit of any company ahead of protecting the environment," Corbett said.
The candidates also expressed conflicting views about gay rights and school choice, but broke no new ground barely two weeks before the Nov. 2 election.
Onorato said he would support an amendment to the Pennsylvania Human Relations Act to outlaw discrimination based on sexual orientation, while Corbett said stricter enforcement of existing laws would be more effective.
"I don't know that an amendment ... will make enforcement any better," Corbett said.
Corbett said he wants to allow students in failing schools to transfer to private or religious schools using vouchers financed by tax money now earmarked for public schools. Onorato said he supports a "limited grant program" that would allow low-income students to escape failing schools but would not make any shift in public school funding.
Corbett, who has directed a high-profile, ongoing investigation into corruption in the Legislature, has maintained a lead since the May primary. A Muhlenberg College poll earlier this month showed Onorato trailing by 11 percentage points.
Corbett also holds an advantage in fundraising. As of Sept. 13, his campaign had $7.7 million on hand, more than double Onorato's total.
The debate was sponosored by 6abc and the Pennsylvania League of Women Voters.