OUR LONG NATIONAL DAYDREAM: A Political Pageant of the Reagan Era by Sidney Blumenthal (Harper: $10.95). A senior editor at The New Republic, Sidney Blumenthal examines some of the contradictions of Ronald Reagan’s presidency: He failed to implement the programs he most vigorously espoused; he frequently misused and misunderstood facts, yet no one seemed to care; in polls, most Americans disagreed with the political credo of the man they elected by overwhelming majorities. Blumenthal seems dismayed by these paradoxes: “His campaign is driven by ideology without ideas . . . The President extols traditional values, but he exists on production values. Voters believe they agree with him on issues, even when they don’t; his talent is to get them to convince themselves . . . His triumph is one of manner over matter.” The essays that discuss previous administrations and the ill-fated Democratic attempts to unseat Reagan in 1984 compound fact with clear-sighted analysis, as Blumenthal excoriates the President for his deliberate misinterpretations of history. “Daydream” suggests that as Reagan’s genial media presence recedes, his administration is already becoming a enigma for historians.