Charles Kopp, a lawyer at Cozen O'Connor and former leader of what was once a top Philadelphia-based law firm, died unexpectedly in his sleep Wednesday.

Kopp, a longtime leader at now-defunct Wolf Block, was 86 years old.

While he spent nearly the last decade of his life as senior counsel at Cozen O'Connor, Kopp spent the bulk of his career at Wolf Block. When the latter firm dissolved, its lawyers dispersed to a number of other law firms, including a large group that went to Cozen O'Connor.

Kopp joined Wolf Block in 1960, and practiced there until 2009. He served multiple terms as either a chairman or co-chairman of the firm, and he led its tax department for years.

“Charlie was at the helm of Wolf Block and saw Wolf Block grow during the years when Wolf Block was the juggernaut law firm in the city of Philadelphia,” said Jim Schultz, Cozen O'Connor's government and regulatory chair.

Schultz said he met Kopp in 2005, and quickly came to see him as a mentor. He had turned to Kopp for advice as recently as last week, he said.

“When you pick up the phone and call Charlie and hit him with a scenario, there's just not much he hasn't seen,” he said. “I know I'm not alone in saying that. He's had that same impact on so many others throughout his career.”

Mark Alderman, a longtime colleague of Kopp's and chairman of Cozen O'Connor Public Strategies, said in a statement that Kopp was “one of a kind.”

“There are brilliant lawyers and there are brilliant strategists, but rarely is such brilliance found in a single person. Add to that a gift for teaching and a love of humor and you have Charlie Kopp,” Alderman said.

Those who called on Kopp for advice include a number of politicians, from the city level to the federal level.

Kopp was a well-known adviser in the Republican party. Throughout the last several decades he was tapped by various government officials for a number of posts, including as a member of Gov. Dick Thornburgh's Special State Tax Commission, co-chair of the Philadelphia Tax Committee under Mayor William Green, commissioner of Delaware River Port Authority, and chairman of the Philadelphia Regional Port Authority. In 1988, he served as a member of Pennsylvania's Electoral College, which elected President George H.W. Bush.

He also served on the Federal Judicial Nominating Commission for the Eastern District of Pennsylvania from 1999 to 2009.

In a statement, former Pennsylvania Gov. and Philadelphia Mayor Ed Rendell said Kopp was “a great Philadelphian.”

“Charlie Kopp was a mainstay of the state's Republican Party and one of its biggest fundraisers, but he always put the city of Philadelphia first,” Rendell said. “When I was mayor, I would often call him for help in Harrisburg on legislation that was important to the city. He never hesitated; he always went to bat for the city and was usually successful in persuading Republicans to support our initiatives.”

Former Gov. Tom Corbett, in a statement, also cited Kopp's love of Philadelphia, and noted that Kopp served as a senior counsel to him on issues affecting Southeastern Pennsylvania, without pay.

“That counsel was invaluable. Philadelphia and Pennsylvania have lost a great, quiet leader today,” Corbett said.