Sen. John McCain (R-Ariz.), whose military experience and ties would be the deepest of any president since Gen. Dwight Eisenhower, would seem a lock to have the backing of the multibillion-dollar defense industry in his White House bid. But many contractors worried about the Arizona Senator’s reform talk and penchant for opposing Congressional earmarks are backing Sen. Barack Obama (D-Ill.) for president.

According to the nonpartisan Center for Responsive Politics, at the end of July Obama had raised $410,443 from supporters associated with the defense companies, while McCain had received $393,954.

“On paper, John McCain should be the favorite” with the defense sector, said Massie Ritsch, the center’s communications director. “So for whatever reason, he is not following the predictable path.” Ritsch added that Republican presidential candidates normally receive about 60 percent of all defense contractor dollars.

John Lehman, a former Navy secretary who’s frequently mentioned as a possible Defense Secretary under McCain, said there’s no question McCain would target weapons spending. “I think everything is on the table. There have go to be tradeoffs [in the Defense budget],” said Lehman, a top national security adviser to the McCain campaign.

Lehman said Defense Secretary Donald Rumsfeld initially sought to take on out-of-control weapons spending, but he was sidetracked by the 9/11 attacks and the Iraq War. He said a McCain Pentagon would likely renew those efforts, along with pushing other business reforms, including cutting civilian personnel and limiting costly changes to defense contracts after they are awarded.

Speaking at the Veterans of Foreign Wars Convention in Orlando, Fla., last month, McCain vowed to fight earmarks if elected and veto any spending bill that contains them. The annual Defense spending bill has traditionally contained more earmarks than any other appropriations measure.

McCain declined to comment for this article.

Contractors have also not forgotten that McCain helped derail a multibillion-dollar tanker aircraft deal between Boeing and the Air Force several years ago. Ultimately, McCain’s efforts helped send a top Air Force procurement official and Boeing executive to jail and led to increased scrutiny and new limits on some defense contracts.

As the top Republican on the Senate Armed Services Committee, McCain has not only targeted Air Force weapons. He has also questioned the Army’s plan for building the multibillion-dollar Future Combat System and expressed frustration with the Navy over soaring shipbuilding costs.

Despite McCain’s promise to keep U.S. troops in Iraq as long as necessary — a move that likely would keep money flowing to the Pentagon — several lobbyists said they are nervous that he would target weapons programs and halt Congressional earmarks that have proved lucrative for both contractors and the Pentagon.

One defense lobbyist who is backing Obama said, “Everyone is nervous about McCain coming in; he is unpredictable. He wants to wield the big hammer about premier military power and then spew how defense companies are taking the American people for a ride.”

Critics of McCain say the prime concern is his “attack dog” mentality could lead to a shake-up in the top ranks on the Pentagon.

“We’re afraid of more regulations and the unknown,” a defense lobbyist said. “The big fear is not what he wants to do or how he will act, but he never gives up. It’s both a virtue but a bane to those on the wrong side of the issue with him.”

One Capitol Hill veteran agreed that McCain would make changes at Defense Department but said that would happen with any new administration.

“There would be a reorganization. There always is,” the former staffer said. “If McCain takes over the people who are there are gone, no senior officials will hold over.”

Joe Carnevale, a senior defense adviser at the Shipbuilders Council of America, cautioned against a massive reorganization regardless of who is elected, warning it would only delay weapons work. “In my mind a reorganization results in kicking the can down the road,” Carnevale said.

George Cahlink of CongressNow contributed to this report.