James P. Herzog, 39, a national political reporter for the Scripps-Howard News Service, died of cancer Aug. 9 at his home in Bethesda.

Mr. Herzog, an award-winning journalist, had covered the White House since the beginning of the Reagan presidency. He was on a presidential trip to an economic summit meeting in Ottawa a year ago when he discovered the first symptoms of the disease. He continued working until June.

In a letter sent yesterday to Mr. Herzog's wife, Margot, President Reagan said, "Jim exemplified the best of his profession. We'll miss him, his sense of humor, his warmth and most of all his friendship."

Mr. Herzog, who was born in Stamford, Conn., graduated from Grinnell College in Iowa and the Columbia University Graduate School of Journalism. He served for two years in the Peace Corps in Tunisia and taught at Cuyahoga Community College in Cleveland before joining the staff of the Akron Beacon Journal in 1970.

While in Akron, he was part of a team of reporters that won the Pulitzer Prize for coverage of the Kent State shootings. He also won a conservation writers' award for his coverage of strip mining.

In 1972, Mr. Herzog joined the Louisville Courier-Journal, where he covered local government and was an investigative reporter. He moved to Washington in 1976 as a reporter for the Courier-Journal's bureau here. In 1977, he went to work for Scripps-Howard and joined its national staff in 1978.

In addition to his wife, of Bethesda, survivors include two sons, Timothy and Nicholas, and two stepsons, David and Andrew Crossland, all of Bethesda; his parents, Mr. and Mrs. Robert Herzog of Stamford, a brother, John Herzog of Dakar, Senegal, and a sister, Sara Hogan of Fanwood, N.J.