McCain, R-Ariz., the presumptive GOP presidential nominee, began championing the deal after an Arizona rancher and his partners hired lobbyists that included members of McCain's congressional staff, his 1992 Senate campaign staff as well as a major donor, the Post reported Friday.

When McCain's legislation was signed into law in November 2005, the ranch owner awarded the construction of up to 12,000 to SunCor Development, a firm run by McCain supporter and fundraiser Steven Betts. Betts and McCain's office told the Post the two never discussed the deal.

"At no time during the consideration of this legislation was there any involvement by officials of SunCor," McCain spokesman Brian Rogers wrote in response to Post questions.

The Audubon Society said the exchange -- totally more than 55,000 acres -- is the largest in Arizona history and includes desert woodland and pronghorn antelope habitat. While the bill called for the parcels to be of equal value, a forestry official expressed concern during a congressional committee meeting that "the public would not receive fair value" for its land.

A formal appraisal hasn't begun, the Post reported.