President Barack Obama has ordered that U.S. flags around the world be flown at half-staff on Tuesday in honor of former Sen. Arlen Specter, who died Sunday at the age of 82.

"By the authority vested in me by the Constitution and laws of the United States of America, that on the day of his interment, the flag of the United States shall be flown at half-staff at the White House and upon all public buildings and grounds," the president stated in his proclamation.

Earlier, Pa. Gov. Tom Corbett ordered state flags at the Capitol and at all other state facilities be lowered to half-staff until sundown Tuesday, the day of Specter's funeral.

Specter died at his home in Philadelphia after a battle with non-Hodgkin lymphoma.

Specter served 30 years in the Senate and is remembered as a pugnacious and prominent former moderate who played starring roles in Supreme Court confirmation hearings. He also is credited with the single-bullet theory in President John F. Kennedy's assassination.

"I think he liked the idea that people saw him as tough. He was tough," said Adrienne Baker-Green, an Allentown native who worked closely with Specter for 13 years, first as his legal counsel in Washington, D.C. and then as the head of his state offices.

Baker-Green described her time with Specter as an education.

"He never wasted a minute. He came in early and stayed late," she said. "It was incredible training."

Despite his often tough exterior, Specter had a soft side, said Baker-Green, recalling a life-threatening accident involving her mother, former Lehigh County Executive Jane Baker, in 2000.

"Senator said, 'Do what you need to do. I'll see you when I see you,'" Baker-Green recalled. "I came back a month later, and my job was waiting for me."

Specter also had a wicked sense of humor. Known for standup acts in Washington, D.C. and Philadelphia, Specter first performed for his staff.

"He'd test his jokes on us. Sometimes they'd fail, sometimes they were good," recalled Baker-Green, who also noted that Specter loved Frank Sinatra and would often sing his songs in the car. "He could carry a tune. Wasn't painful, but good."

Hank Barnette, the former CEO of Bethlehem Steel and a friend of Specter, said the two men would play squash, even when Specter was going through chemotherapy.

That didn't come as a surprise to Baker-Green, who said Specter's theme song easily could have been "My Way."

"They don't make them like Arlen Specter," she said. "So, fact he's not with us anymore is sad."

Specter had few regrets and always looked ahead, but he was very disappointed when his re-election bid in 2010 came up short, Baker Green said.

Specter's funeral is scheduled for Tuesday in Penn Valley, Pa. Vice President Joe Biden is scheduled to attend.