WASHINGTON - Sen. John McCain said yesterday that his inquiries into a $35 billion Air Force tanker contract were designed to ensure an evenhanded bidding process and denied they were motivated by lobbyists who are close advisers to his presidential campaign.

"I had nothing to do with the contract, except to insist in writing, on several occasions as this process went forward, that it be fair and open and transparent," he said at a meeting with voters in St. Louis.

His remarks came after the Associated Press reported that some of his current advisers lobbied last year for European Aeronautic Defence & Space Co., the parent company of the plane-maker Airbus.

EADS and its U.S. partner, Northrop Grumman Corp., beat Boeing Co. for the lucrative aerial refueling contract.

Boeing yesterday filed a formal protest of the tanker award with the Government Accountability Office, citing "irregularities" in the contract competition.

Two of the lobbyists working on the EADS account gave up their lobbying work when they joined McCain's campaign last year. A third, former Texas Rep. Tom Loeffler, lobbies for EADS and serves as McCain's national finance chairman.

McCain, the Republican presidential nominee in waiting, has been instrumental in the Pentagon's long attempt to complete a deal on the tanker. He helped block an earlier, scandal-marred tanker contract with Boeing in 2004 and prodded the Pentagon in 2006 to change proposed bidding procedures opposed by Airbus.

EADS retained Ogilvy Government Relations and the Loeffler Group to lobby for the tanker deal last year, months after McCain sent two letters urging the Defense Department to make sure the bidding proposals guaranteed competition between Boeing and Airbus.

"They never lobbied him related to the issues, and the letters went out before they were contracted" by EADS, McCain campaign spokeswoman Jill Hazelbaker said.

According to lobbying records filed with the Senate, Loeffler Group lobbyists on the project included Loeffler; Susan Nelson, who left the company and is now the campaign's finance director; and former Secretary of the Navy William Ball 3d, who has campaigned for McCain.

Ogilvy lobbyist John Green, who was assigned the EADS work, recently took a leave of absence to volunteer for McCain as the campaign's congressional liaison.

"The aesthetics are not good, especially since he is an advocate of reform and transparency," said Richard Aboulafia, an analyst with the aerospace consulting firm Teal Group.

McCain said yesterday his work on the tanker was designed to keep the bidding competitive.

"I think my record is very clear on this issue, including a paper trail of letters that we wrote to the Department of Defense during this process and saying clearly and unequivocally we just want a fair process," he told reporters in St. Louis.

McCain is a longtime critic of influence-peddling and special-interest politics. He has come under increased scrutiny as a presidential candidate, particularly because he has surrounded himself with advisers who are veteran Washington lobbyists.

On the Air Force tanker deal, he has portrayed himself as a neutral watchdog.

It is unclear what EADS hired the lobbyists to do. Loeffler officials did not respond to phone and e-mail messages.

Boeing supporters already have begun to accuse McCain of damaging Boeing's chances by inserting himself into the tanker deal.

Rep. Norm Dicks (D., Wash.) said the field was "tilted to Airbus" because the Pentagon did not weigh European subsidies for Airbus in its deliberations - a decision he blamed on McCain. Everett, Wash., is where Boeing would perform much of the tanker work.