CARROLLTON, Ga. — In an unnoticed 1992 speech, Newt Gingrich in a single utterance took aim not only at a beloved conservative icon but also at a core tenet of the conservative movement: that government must be limited.

Ronald Reagan’s “weakness,” Gingrich told the National Academy of Public Administration in Atlanta, was that “he didn’t think government mattered. . . . The Reagan failure was to grossly undervalue the centrality of government as the organizing mechanism for reinforcing societal behavior.”

A review of thousands of documents detailing Gingrich’s career shows it wasn’t the first time he had criticized Reagan, whom he regularly invokes today in his campaign for the Republican presidential nomination. When Gingrich was in the House, his chief of staff noted at a 1983 staff meeting that his boss frequently derided Reagan, along with then-White House Chief of Staff James A. Baker III and Robert H. Michel, the House Republican leader.

Gingrich “assumed that he’s the whole Republican Party,” said the Gingrich aide, Frank Gregorsky, according to a transcript of the meeting. “He knows more than the president, the president’s people, Michel, Baker. He calls them stupid all the time, and I think that’s going to get him into big trouble someday.”...