McCain, R-Ariz., assigned an aide to help Donald Diamond, an Arizona real estate mogul, to buy land at the Fort Ord military base in Monterey Bay, Calif. When Diamond ran into development issues with city council members, McCain stepped in, endorsing Diamond in a letter as "a close personal friend," The New York Times reported Tuesday.

Diamond is a top fundraiser, or Innovator, for McCain's presidential bid, bringing in more than $250,000. The McCain campaign touts its distance from special interest groups, but the Times raises questions by pointing out Diamond turned a $20 million profit from the deal.

McCain also backed two laws in 1991 and 1994 that resulted in Diamond earning millions of dollars by selling acreage to national parks.

Jill Hazelbaker, a McCain spokeswoman, said the senator "had done nothing for Mr. Diamond that he would not do for any other Arizona citizen," adding the land-exchange laws had the support of local leaders and environmental groups.

Diamond, who serves on the finance committee for the McCain camp, said the Arizona senator was doing his job.

"I think that is what Congress people are supposed to do for constituents," he said.