Rep. Joe Sestak's payroll has emerged as a potential wedge issue in the Democratic primary for the U.S. Senate, with Sen. Arlen Specter demanding that Sestak explain why a majority of his campaign employees appear to earn less than the minimum wage of $7.25 an hour.

"How can you make laws if you don't follow them yourself?" Specter said in a news release yesterday. "Joe needs to answer a basic question: Has he obeyed the state and federal minimum-wage laws?"

According to Specter's campaign, Federal Election Commission reports show that 10 of the 16 Sestak campaign workers employed during the last three months of 2009 received less than $7.25 an hour, based on the assumption of a 40-hour workweek. In one case, an employee earned the equivalent of $2.23 an hour, the Specter campaign said.

Several experts in labor law contacted yesterday said that minimum-wage requirements probably applied to political campaigns.

After a campaign stop in Philadelphia yesterday, Sestak said Specter was pushing the issue to camouflage a record, as a longtime Republican senator, of supporting policies hostile to working families.

"It's dishonest, it's negative, and it's just the type of politics Pennsylvanians don't want to have anymore," Sestak said.

Asked whether he believed his campaign was in compliance, Sestak said: "We're doing everything right," without addressing specific questions raised by his opponent's analysis of the campaign expenditure reports.

"People come to us, we give them health care [coverage] and other things, we offer them a stipend," Sestak said. Asked directly whether he was paying the workers a stipend rather than a salary, he said: "Whatever term you want to use."

He was visiting the Sunday Breakfast Rescue Mission in Philadelphia to receive the endorsement of Vets Vision, an organization that battles homelessness among military veterans.

At the event, Rep. Eric Massa (D., N.Y.) also endorsed Sestak, with whom he served in the Navy; Sestak is a retired admiral.

Specter, first elected to the Senate in 1980 as a Republican, is seeking a sixth term - as a Democrat. He switched parties last year and faces a primary challenge from Sestak.

Their battle has turned sharply personal in recent days as Specter's campaign has pushed the wage issue, seeking to undercut Sestak's claims to be the champion of workers. And Sestak's campaign has contended that Specter is guilty of "flat-out perjury" in stating that he had a nearly perfect pro-labor record.

Sestak's campaign yesterday noted Specter votes against raising the minimum wage in 1999 and 2005 - though he has cast other votes in favor of such increases - and noted that Specter supported the tax-cut policies of President George W. Bush, which benefited the wealthiest Americans.

The Specter campaign is planning today to launch a Web site, NoDoughJoe.org, to highlight what it says are the low salaries on Sestak's team.

The federal Fair Labor Standards Act requires that workers be paid a minimum wage, as well as overtime, unless they or their industries are exempted from the law. Exemptions include seasonal agricultural workers; seasonal work in amusement parks and children's camps; and fishing.

People employed in executive, administrative, and professional jobs are also exempt from the act, as are computer programmers and other IT workers.

"A campaign organization is just like any other nonprofit, public-sector enterprise and has to pay workers in accordance with the federal and state wage and hour laws," said George A. Voegele Jr., an employment lawyer with the Cozen O'Connor law firm.

"A high-level policy adviser or campaign manager, anybody involved in strategy is probably going to be exempt," Voegele said.

The regional office of the U.S. Department of Labor, when asked to clarify the matter, yesterday produced a 1977 advisory letter that said workers for political committees should be covered by the federal law unless they were volunteers or working in an executive or professional position.

Volunteers for nonprofits, such as a political campaign, may receive a nominal fee or a travel allowance, said Sharon Farmer, a labor lawyer with Ballard Spahr L.L.P. But an organization cannot classify workers as volunteers "in order to justify paying below-market wages," Farmer said. There is, however, no specific dollar figure specified to separate volunteers from employees, she said.

Payments to volunteers usually are listed on FEC reports as reimbursements for expenses or travel allowances.

An agreement between an employer and an employee can't get around the requirement for a minimum wage. "You can't waive your rights" under the Fair Labor Standards Act, Farmer said.

Pennsylvania's minimum wage is also $7.25, and the state allows exemptions similar to those provided in the federal law.

Troy Thompson, a spokesman for the state Department of Labor & Industry, said that campaign employees must be paid "at least the minimum wage unless they are otherwise exempt by law."

Sestak said that Specter was unfairly "using language that makes people think I'm a criminal."

Contact staff writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com.