Donald S. Dawson, who as a presidential aide marshaled Harry S. Truman's crucial whistle-stop tour in the 1948 election campaign and who later had a long career as a Washington lawyer, died on Sunday at his home in Bethesda, Md. He was 97.

Mr. Dawson was personnel director of the Reconstruction Finance Corporation, created by the government to help fight the Depression, when Truman took him on in 1947 as a special executive assistant. He became perhaps the nation's first modern political advance man, acting as ubiquitous scout and troubleshooter, a master of the subtle but insistent politics that characterized the president's bid for a full term in the White House and became essential ingredients for many other successful campaigns thereafter.

The whistle-stop that Mr. Dawson organized and commanded was a 22,000-mile cross-country stumping on the rails in which Truman, widely expected to be defeated by the Republican challenger, Gov. Thomas E. Dewey of New York, gained victory with a relentless attack on the Republican-controlled Congress.

"My job was to be a jump ahead, getting kids out of school early, finding free buses, whatever it took," Mr. Dawson told The New York Times in 1992, reminiscing in his law office a short walk from the White House. "When the president caught up with me at each stop, I'd brief him on the local situation, and he'd quickly adapt his direct comments. His spur-of-the-moment stuff was so good. He always wanted to talk about things the people wanted to know. Wonderful."

"If the boss saw 20 people out of the window, he'd stop the train," Mr. Dawson told his interviewer. "The back platform of the train is where he really hit the people. Off the cuff, he was the best. And he was never afraid of politics."