Specter, R-Pa., used a process called "earmarking" 13 times to set aside $48.7 million for six clients represented by lobbyist Michael Herson and the firm he co-founded, American Defense International. The clients paid Herson's firm nearly $1.5 million in fees since 2002, federal lobbying records show.

Herson's wife, Vicki Siegel Herson, is Specter's legislative assistant for appropriations. She deals with Specter's work on the Senate Appropriations Committee and its defense subcommittee, where all the earmarks originated. Siegel, who uses her maiden name at work, is a former lobbyist for defense contractors who has worked for Specter since 1999.

Earmarks are a way for powerful members of Congress to specify how federal money must be spent. They have been the subject of attention on Capitol Hill because they played a role in recent scandals, including the bribery conviction of former representative Randy "Duke" Cunningham, R-Calif.

Sen. John McCain, R-Ariz., a longtime critic of earmarks, introduced legislation last week to curb the use of earmarks. The 2005 federal budget included 15,877 earmarks for $47.4 billion in spending, according to a Congressional Research Service study that McCain requested.

In a statement responding to questions from USA TODAY, Specter said he did not know the earmarks were going to clients of Siegel's husband. "I am advised that at no time did her husband lobby my office or seek appropriations from any member of my staff," the statement said. Specter declined to be interviewed.

Specter claimed credit for all the earmarks in news releases, noting the projects' ties to Pennsylvania. "These projects, key to our nation's defense, will be invaluable in our continuing war on terror," a Dec. 22 press release said in announcing $56 million worth of earmarks, including $17 million for four Herson clients.

The earmarks paid for research, software and oxygen masks. The largest of the earmarks — $11 million in fiscal 2005 and $6.5 million in fiscal 2006 — went to Drexel University for an initiative to link the military's computer systems.

Senate ethics rules prohibit senators and their staffers from using their positions to further their personal financial interests. Taking official action in return for money or other benefits is illegal. Ethical issues arise more frequently than criminal cases, said Jan Baran, a Washington lawyer who has handled several ethics cases. "Usually these types of situations are political and not legal issues," he said.

Siegel did not return telephone and e-mail messages about her role in the earmarks and if she recused herself from matters involving her husband's firm.

Herson said neither he nor anyone from American Defense International had lobbied Siegel or anyone in Specter's office. "I do not set foot in Specter's office as a lobbyist," Herson said.

Herson said he contacted members of Congress from New Jersey about clients who got earmarks. Neither New Jersey senator is on the Appropriations Committee, where the earmarks originated.

"Even when there is nothing improper about the actual earmark, it's very difficult for citizens and even other members to be sure," said Dennis Thompson, who teaches ethics at Harvard University.