HARRISBURG (AP) Common ground is scarce in the Pennsylvania governor's race, the only statewide election contest in 2014.

Republican incumbent Tom Corbett is battling chronically weak polling numbers despite first-term accomplishments that include erasing a multibillion-dollar budget shortfall without major tax increases and signing a transportation-improvement program that has jump-started highway and bridge projects stalled for years.Independent polls show Democratic businessman Tom Wolf, a former state revenue secretary, maintaining a double-digit lead as he presses a liberal agenda in a generally moderate state.The candidates' sharply contrasting views should spur voter interest and crowd the airwaves with dueling TV attack ads as Labor Day unofficially launches the campaign for the Nov. 4 election.TAXES: Corbett, formerly the state's elected attorney general, thinks taxes should be minimized as much as possible. Wolf views taxes as tools for shaping public policy.Corbett promised in his 2010 campaign that he wouldn't increase taxes or fees. But after he was elected, he raised a wholesale tax on gasoline as well as scores of motorist and vehicle fees to finance the $2.3 billion transportation bill. And with another potential multibillion-dollar shortfall looming for next year, Corbett isn't renewing the no-new-taxes pledge for his second term.The centerpiece of Wolf's tax plan is an overhaul of Pennsylvania's $12 billion-a-year income tax that would shift more of the burden to the wealthy, reduce taxes for many middle-income households and add many lower-income filers to the 20-plus percent that already pay no tax. Wolf has not disclosed some important details about his plan, such as the amount of an expected increase in the current tax rate.EDUCATION FUNDING: Corbett's re-election campaign is still hounded by the nearly $900 million reduction in state aid to public schools that he approved in his first budget in 2011. Corbett blames the reduction on expiring federal stimulus funds he says never should have gone to school districts' operating budgets. Corbett has increased state spending for public schools in each of the last two budgets. He has sought unsuccessfully to clear the way for more privately run, publicly funded charter schools by vesting approval authority in a state board rather than local school boards. A compromise after Corbett's failure to win a sweeping new voucher program was an extra $75 million a year in tax credits that largely benefit private and parochial schools.In keeping with his tax-shifting approach, Wolf proposes to increase the state's share of public school spending from the current one-third to one-half a jump of several billion dollars a year in exchange for a dollar-for-dollar reduction in property taxes levied by the state's 500 school districts. Wolf has said the additional state money would come primarily from the revamped income tax and a new tax he proposes on gas drilling. Wolf also proposes creating a state agency to scrutinize finances and academics at charter schools and cybercharters while leaving charter school approval authority with the school boards.PENSIONS: Corbett says the burgeoning cost of Pennsylvania's public pensions is a crisis that requires prompt, decisive action. Wolf argues that it's a problem that can be resolved in the years ahead.Corbett wants to scale back pensions for future school and state employees as a meaningful step toward savings. He says the taxpayers' share of the pension costs for current employees $2.1 billion this year is crowding out funding for other programs and helping drive up local property taxes.Wolf contends that the pension problems are partly the result of the state contributing less than its fair share of the costs for nearly a decade and that a 2010 law reducing pension promises to future employees and refinancing existing obligations needs more time to work.GAS DRILLING: The Marcellus Shale drilling boom made Pennsylvania the nation's No. 2 producer of natural gas and Wolf is eager to do something Corbett has steadfastly refused to do tax it.Wolf proposes levying a 5 percent extraction tax on gas production that is expected to generate about $1 billion, most of which would be available for public education and other programs. Pennsylvania is the only major gas-producing state without such a tax.Corbett opposed efforts to impose an extraction tax, saying it would be an obstacle to the growth of a major new industry that is providing good-paying jobs in economically struggling areas. But he backed legislation authorizing counties to levy an "impact fee" that generated about $225 million last year, mainly to benefit counties and municipalities that host gas wells.HEALTH CARE FUNDING: Corbett claimed victory in the debate over how the Medicaid expansion provided by the 2010 federal health care law should be administered in the state, but critics say he needlessly delayed health care for a half-million low-income Pennsylvanians.