State Sen. Mike Stack is weighing whether to hold on to his Northeast Philadelphia seat if he is elected lieutenant governor on Nov. 4.

If he did, it would be only the third time someone has straddled both positions, and the first time by an elected lieutenant governor.

Asked about the possibility Wednesday, Stack, a Democrat, declined to dismiss it, but said he was focused on being elected lieutenant governor. Stack, who represents the Fifth District, is running against Republican Lt. Gov. Jim Cawley.

"I'm not counting it out," he said. "It will be something that needs to be discussed and addressed, but first things first."

He went on to say, however, that anyone considering a run for his Senate seat might be jumping the gun.

"I think it is premature for people to be lining up to succeed me as senator," Stack said. "My term does not end until 2016. I don't think there necessarily should be a rush to fill the seat."

U.S. Rep. Robert Brady, chairman of the Democratic City Committee, said Stack had spoken to him about holding both jobs.

"He said he was consulting constitutional lawyers to see if it was legal," Brady said. "I don't know that it is. What would happen? Would he be paid both salaries?"

Stack noted that on two occasions in the past, a state senator also served as lieutenant governor. Both involved the president pro tempore of the Senate rising to the lieutenant governor's post when it was vacated in midterm.

In 2001, State Sen. Robert Jubelirer took over as lieutenant governor when Mark Schweiker rose to governor to replace Tom Ridge, who had been appointed director of homeland security. Jubelirer held both offices until Schweiker's term expired in January 2003. Jubelirer left the Senate in 2006.

State Rep. John Lawless (D., Montgomery) and two political activists from Blair and Armstrong Counties filed a lawsuit challenging Jubelirer's dual roles. Commonwealth Court ruled 6-1 in favor of Jubelirer, and the state Supreme Court affirmed the decision without an opinion.

In 2008, with the death of Lt. Gov. Katherine Baker Knoll, Senate President Pro Tempore Joseph B. Scarnati rose to the position. He held both posts until Knoll's term expired in 2011.

Bruce Ledewitz, a Duquesne University law professor and expert in Pennsylvania constitutional law, said Stack's position is not analogous to those of Jubelirer and Scarnati, in that they were constitutionally mandated to fill the vacant post.

He doubted that the courts would support Stack if he chose to hold on to his Senate seat after being elected lieutenant governor.

The state constitution specifically states that "no senator or representative shall, during the time for which he was elected, be appointed to any civil office under this commonwealth to which a salary, fee or perquisite is attached."

That should preclude Stack from holding both jobs, Ledewitz said.

Jubelirer, who is now in private practice, said he also believed the constitution would be an impediment. In answer to Brady's concerns, he said that during the time he served in both roles, he accepted only the salary of lieutenant governor.

Jubelirer also anticipated a concern of former Gov. Ed Rendell, who noted that as lieutenant governor, Stack would be called upon to provide the deciding vote should there be a tie among the Senate's 50 members. Does that mean Stack would have two votes? Rendell asked rhetorically.

Jubelirer said he never faced that situation, but assumed he would have been permitted only one vote.

Either way, Rendell shared company with Jubelirer and Ledewitz when it came to the legality of Stack's holding both positions simultaneously.

"I find it inconceivable that the law would allow that to happen," he said.