Pennsylvania's candidates for governor raised almost $18 million over the summer from well-heeled donors and special interest groups, according to campaign finance reports filed Tuesday with the state.

Gov. Corbett's biggest donor, the Washington-based Republican Governors Association, gave him $4 million in the three months that ended Sept. 15 in monthly installments, the reports showed.

Democratic challenger Tom Wolf, a York businessman, received about $2.9 million from labor unions in the three-month period, including $500,000 from AFSCME, which represents public employees, and $100,000 from the Pennsylvania State Education Association, the teachers' union.

Wolf received $250,000 from the Democratic Governors Association, and $1 million from Thomas Grumbacher, chairman of the Bon-Ton department store chain, based in York.

Investor and conservative activist John M. Templeton of Bryn Mawr, the largest individual donor to Corbett, chipped in $400,000. Natural-gas magnate Terrence M. Pegula gave $250,000.

There are no contribution limits in Pennsylvania state races.

Overall, Wolf's campaign raised $9.6 million during the period and spent more than $6.2 million, leaving about $6.5 million on hand. Corbett raised $8 million, spent the same, and had about $4.8 million on hand.

All told, Corbett has raised nearly $25 million overall and spent about $20 million. Wolf has reported raising nearly $28 million, including at least $11 million from himself and his family during the Democratic primary. He has spent about $21 million.

The Campaign for a Fresh Start, a political action committee supporting Wolf and Democratic legislative candidates in targeted races, reported raising $243,070. It spent $136,751 and had $106,319 on hand by Sept. 15.

The PAC, chaired by Wolf's former primary rival, Katie McGinty, was established in late June and had not previously been required to file a report.

Most of Fresh Start's contributions came in large chunks from allied PACs. It received $50,000 from Local 98 of the Electricians union, headed by Philadelphia power broker John "Johnny Doc" Dougherty; $40,824 from the Democratic Governors Association; and $55,000 from the Wolf campaign.

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This article contains information from the Associated Press.