Leahy, who target shoots on his Vermont farm, is from a state with a strong gun-rights tradition.
"It is so hard to find out what works best," Leahy said in a recent telephone interview with The Associated Press. "Every state is different. What works (in Vermont) is not going to work in Chicago or New York City. How do we balance that?"
It's not Leahy's first balancing act. He's often tangled with Republicans in battles over Supreme Court and other judicial nominees over the years. Leahy was a leader in the Judiciary Committee's investigation into the mass firings of U.S. attorneys during the Bush administration.
A former prosecutor in Vermont, Leahy has been active on human rights, privacy and environmental issues.
He's crusaded against the production, export and use of antipersonnel land mines and wrote the first law banning the export of mines that pose a danger to civilians. He championed the law prohibiting U.S. aid to units of foreign security forces that commit gross violations of human rights.
While his partisan bent can get under the skin of Republicans, Leahy has friends across the aisle.
"He's controversial over here," said Cochran. "He's very partisan. But he's effective."
Their friendship was forged partly in the snows of Vermont one winter after Leahy persuaded his southern colleague to visit for a congressional field hearing. Cochran said he'd never seen snow that deep.
"I thought he was trying to kill me," Cochran recalls.
Cochran returned the favor, inviting Leahy to a summertime event in steamy Mississippi.
"He nearly died with the heat," Cochran said.
While most Senate office walls are plastered with photos of lawmakers posing with presidents and celebrities, Leahy's office features his own intimate shots from his travels along with some behind-the-scenes glimpses of widely seen events like inaugurations and White House bill-signing ceremonies. Some photos have been used in national publications.
The one directly above his desk is a stark black-and-white photo of a man with pleading eyes that Leahy took at a refugee camp in El Salvador in 1982. Leahy calls it his "conscience photo" and offers an interpretation:
"I look at that man with the stubble on his face, and he's saying, 'If I was rich and powerful, you'd talk to me. What do you do for people like me?'"