David Gergen, an inside-the-Beltway veteran who helped shape the public images of four presidents, mostly Republicans, and who, after a turn as a magazine editor, trod a well-worn path from political insider to television commentator, died on Thursday at a retirement community in Lexington, Mass. He was 83.

His son, Christopher, said the cause was Lewy body dementia.

It was Mr. Gergen who devised a line in the 1980 presidential election that helped secure victory for the Republican candidate, Ronald Reagan, over Jimmy Carter, the incumbent Democrat. In that era of high inflation, onerous interest rates and a national psyche wounded by Iran’s holding of 52 Americans hostage, Mr. Carter was already on the ropes. The clincher came in a televised debate a week before the election when Mr. Reagan asked viewers a Gergen-suggested question that hit political pay dirt: “Are you better off than you were four years ago?”

For many Americans, the answer was no.

“Rhetorical questions have great power,” Mr. Gergen said years later.

“It’s one of those things that you sometimes strike gold,” he said. “When you’re out there panhandling in the river, occasionally you get a gold nugget.”

Mr. Gergen (pronounced with hard G’s) mined as many of those nuggets as he could writing speeches, briefing news reporters, creating communications strategies and helping to set the agenda for four presidents: the Republicans Richard M. Nixon, Gerald R. Ford and Mr. Reagan, and then a Democrat, Bill Clinton.