Carl M. Buchholz, 51, of Flourtown, a Philadelphia lawyer and civic leader who was tapped by President George W. Bush to help create the White House Office of Homeland Security after 9/11, died of cancer Monday, May 23, at his home.

"He was an unmatched leader as well as one of the most dedicated, forthright, and effective colleagues I've had the privilege to work with," said Drexel University president John A. Fry, who knew Mr. Buchholz as a friend and Drexel board member. "He fought hard and bravely over the past year against the disease that took his life."

At the time of his death, Mr. Buchholz was managing partner of the Philadelphia office of DLA Piper International. Before that he was managing partner of Blank Rome.

He was a key member of the Bush-Cheney presidential team that litigated the historic Florida recount in 2000 that led to the defeat of Democratic candidates Al Gore and Joe Lieberman.

After Sept. 11, 2001, Bush appointed Mr. Buchholz to work in the White House as special assistant to the president for homeland security.

Teaming up with former Pennsylvania Gov. Tom Ridge, who was homeland security director, Mr. Buchholz helped develop the administration's response to terrorism. He served as cochairman of the transition team that created the Department of Homeland Security.

A mammoth undertaking, the department consisted of 22 federal agencies and 170,000 employees, fueled by a budget of more than $46 billion.

"During those chaotic early days in the White House after Sept. 11, Carl was always a calm, unflappable professional presence whose sound counsel was invaluable," Ridge said in an email. "He unselfishly left a successful law practice in Philadelphia to serve his nation, and did so with distinction, intelligence, creativity and compassion."

Mr. Buchholz stayed engaged in Republican politics. In 2004, he served as Pennsylvania general counsel to the Bush reelection campaign, and also cochaired the transition team for newly elected Pennsylvania Attorney General Tom Corbett.

Born in Philadelphia, Mr. Buchholz graduated with honors from Wissahickon High School. He received a bachelor of arts degree from the University of Virginia in 1987.

His first job was as a special assistant in the office of U.S. Sen. John Heinz, where he met fellow staff member Karen Dougherty. They were married Dec. 28, 1991, in Potomac, Md.

He returned home to earn a law degree from the University of Pennsylvania in 1992. After graduating, he clerked for U.S. District Judge Anita B. Brody.

In 1993, Mr. Buchholz became an associate for Blank Rome, rising quickly to become a partner in 2000, and was elected managing partner and CEO of the firm in 2006.

For the next five years, he led the 500-lawyer firm through an aggressive growth plan that expanded the firm's national and international profile.

In August 2012, he announced he was joining DLA Piper. He chose the firm because it could accommodate the growing international segment of his client base, he told the Philadelphia Business Journal.

A five-year member of Drexel's board of trustees, he also was active in the Greater Philadelphia Chamber of Commerce, the University of Virginia Jefferson Scholars Committee, the Committee of Seventy, Visit Philadelphia, and the Museum of the American Revolution.

Mr. Buchholz was devoted to the United Way of Greater Philadelphia and Southern New Jersey as a past chairman of the board. In that role, he led a strategy to increase the United Way's community investment, and in early 2015, helped select Jim Cawley, who was lieutenant governor while Corbett was governor, as the United Way's president and CEO.

"Carl believed that a life of professional and business success was only half a life, that you needed to be successful in service to others," Cawley said.

He and his wife served as cochairs of United Way's Alexis de Tocqueville Society. Mr. Buchholz was named United Way's volunteer of the year in 2011.

A gentle and genial man, Mr. Buchholz was grounded in a deep love for his family. The family traveled the world, often with close friends along for the adventure, and spent leisure time at its vacation home on the Eastern Shore in Rock Hall, Md.

"He lit up every time he had the chance to talk about his family," his wife said.

In addition to his wife, who is senior vice president of administration at Comcast Corp., he is survived by son Alex, daughter Julia, a brother, and a sister.

A funeral service is set for 3 p.m. Thursday, June 2, at St. Thomas' Church, Whitemarsh, Bethlehem Pike and Camp Hill Road, Fort Washington.

Donations may be made to the United Way of Greater Philadelphia and Southern New Jersey, 1709 Benjamin Franklin Parkway, Philadelphia 19103; St. Thomas' Episcopal Church Memorial Fund, Box 247, Fort Washington, Pa. 19034; or the Chesapeake Bay Foundation, 6 Herndon Ave., Annapolis, Md. 21403.