The contribution figures come from an analysis by two civic groups, the Conservation Voters of Pennsylvania and Common Cause PA, based on contribution records filed with the state from 2001 through mid-September.
The groups counted $707,220 going to Republican Corbett from gas-related interests, compared to a total of $700,300 to other active state officials and candidates. The gas industry also donated about $660,000 to noncandidate political organizations, most of them tied to the state Republican Party.
"Those contributions have all been reported, they're all legal," Kevin Harley, a spokesman for Corbett, said yesterday.
If Corbett is elected governor, Harley said, he would not hesitate to enforce environmental laws against gas companies, "whether he's gotten a political contribution or not."
But Corbett is opposed to taxes on the gas industry because he thinks it would limit gas development in Pennsylvania, according to Harley.
"Tom Corbett believes that we have to grow the gas industry in a economically and environmentally responsible fashion and that does not include a tax," he said.
Pennsylvania is now the only state with substantial mineral resources that does not levy a severance tax or fee, according to the Pennsylvania Budget and Policy Center, a nonpartisan research agency based in Harrisburg.
The biggest single source of gas-related donations in the Common Cause/Conservation Voters analysis was the S.W. Jack Drilling Co. of Indiana County, whose executives reported $954,000 in state political donations over a 10-year period.
Its chairman and CEO, Christine Toretti, is a Republican national committeewoman who has given heavily to both Republican candidates and party organizations. Shale-gas drilling was not a major part of S.W. Jack's business, and the company ceased operations in August.
But in other respects, the Common Cause/Conservation Voters analysis is likely understated. It does not cover donations or expenditures by out-of-state organizations that have not filed campaign finance reports with Pennsylvania election officials.
And the analysis also leaves out the most important political contribution in Corbett's career - a mysterious $480,000 check delivered in the closing weeks of his first campaign for state attorney general, in 2004.
It was one of the biggest campaign donations in Pennsylvania history. It came from a little-known Washington-based group called the "Republican State Leadership Committee," and its legality was questionable.
The group was not registered as a political-action committee, in either Pennsylvania or Washington. Reports filed with the Internal Revenue Service indicated it had raised more than $9 million over the previous three years - the bulk of it from corporations, prohibited by state law from contributing to Pennsylvania candidates.
State election officials demanded an accounting of where Corbett's money had originated, and the RSLC provided it - but not until a month after the election.
The group said that most of the Corbett money came from a natural-gas executive based in Oklahoma - Aubrey McClendon, chairman and CEO of the Chesapeake Energy Co., who had donated $450,000 to the RSLC in separate donations, around the date it was sending money to Corbett.
As of last month, Chesapeake had obtained 839 Marcellus drilling permits in Pennsylvania, more than any other company, and had drilled at 126 sites, making it the second-biggest operator after Talisman Energy of Alberta, Canada, according to the state's Department of Environmental Protection.